The Biblical Commission answers the following questions: On the Author, Time of Composition and Historical Truth Of the Gospels According to St. Mark and St. Luke
June 26, 1912.

390.
1. The clear evidence of tradition, wonderfully harmonious from the earliest ages of the Church and supported by numerous arguments, viz., by the explicit testimonies of the Fathers and ecclesiastical writers, by the citations and allusions occurring in their writings, by the usage of the ancient heretics, by the versions of the books of the New Testament, by the most ancient and almost universal manuscript codices, and also by intrinsic arguments from the text itself of the sacred books, certainly compels us to affirm that Mark, the disciple and interpreter of Peter, and Luke, a physician, the assistant and companion of Paul, are really the authors of the Gospels which are respectively attributed to them.
Answer: Yes.
391.
2. The reasons, by which some critics endeavor to prove that the last twelve verses of the Gospel of Mark (16:9-20) were not written by Mark himself but added by another hand, are of a kind to justify the statement that these verses are not to be received as inspired and canonical, or at least prove that Mark is not the author of said verses.
Answer: No to both parts.
392.

3. Likewise, it is lawful to doubt of the inspiration and canonicity of the narrations of Luke on the infancy of Christ (chapter 1-2) or on the apparition of the Angel comforting Jesus and on the bloody sweat (22:43-44); or whether at least it can be shown by solid reasons - as ancient heretics used to think and certain more recent critics hold-that these narrations do not belong to the genuine Gospel of Luke.
Answer: No to both parts.

393.
4. The very rare and altogether singular documents in which the Canticle Magnificat is attributed not to the Blessed Virgin Mary, but to Elizabeth, can and should at all prevail against the harmonious testimony of nearly all the codices both of the original Greek text and of the versions, as well as against the interpretation clearly required no less by the context than by the mind of the Virgin herself and constant tradition of the Church.
Answer: No.
394.
5. With regard to the chronological order of the Gospels, it is lawful to abandon the opinion, supported as it is by the most ancient as well as constant testimony of tradition, which testifies that, after Matthew, who first of all wrote his Gospel in his native language, Mark wrote second and Luke third; or is this opinion to be regarded as opposed to that which asserts that the second and third Gospels were composed before the Greek version of the first Gospel.
Answer: No to both parts.
395.
6. Is it lawful to set the date of the composition of the Gospels of Mark and Luke as late as the destruction of the city of Jerusalem; or whether, from the fact that in Luke the prophecy of our Lord concerning the overthrow of this city seems to be more definite, it can at least be held that his Gospel was written after the siege had been begun.
Answer: No to both parts.
396.
7. Must it be affirmed that the Gospel of Luke preceded the book of the Acts of the Apostles (Acts 1:1-2); and since this book, of which the same Luke is author, was finished at the end of the Roman imprisonment of the Apostle (Acts 28:30-31), his Gospel was composed not after this date.
Answer: Yes.
397.
8. Taking present both of the testimony of tradition and of internal arguments, with regard to the sources which both Evangelists used in writing their Gospels, the opinion can prudently be called in question which holds that Mark wrote according to the preaching of Peter and Luke according to the preaching of Paul, and which at the same time asserts that these Evangelists had at their disposal other trustworthy sources, either oral or already written.
Answer: No.
398.
9. The sayings and doings which are accurately and almost graphically narrated by Mark, according to the preaching of Peter, and are most faithfully set forth by Luke, having diligently learned all things from the beginning from eminently trustworthy witnesses, viz., "who from the beginning were eyewitnesses and ministers of the word" (Luke 1 :2-3), have a just claim to the full historical credence which the Church has ever given them; or whether, on the contrary, the sayings and doing are to be regarded as devoid of historical truth at least in part, either because the writers were not eye-witnesses, or because in both Evangelists lack of order and discrepancy in the succession of facts are not infrequently found, or because, since they came and wrote later, they must necessarily have related conceptions foreign to the mind of Christ and the Apostles, or facts more or less infected by popular imagination, or, finally because they indulged in preconceived dogmatic ideas, each according to the scope he had in view.
Answer: Yes to the first part; No to the second.