Sorry you guys don’t get it, but it’s like this:
The Church teaches that Mary, unlike Zachary earlier in Luke chap. 1, did not doubt the angel’s words; hence, from what I’ve been led to understand, the Greek renders it “How shall (or will, if you eschew the “archaic”) this be…?” and not “How can this be…?” the latter implying doubt.
And, of course, the Douay-Rheims and the Confraternity not only got this right, but rendered the rest of the question in a literal manner: “How shall this be done, because I know not man?”
THAT’S the “big deal”.
Thomas A. Nelson’s “Which Bible Should You Read?” (from TAN Books) expounds on this and a lot of other passages; check it out!