Monday is the first day . . . . . . . the week. A. of B. after C. during D. before

of
after
during
before

The correct answer is A. of.

Monday is the first day of the week. It is followed by Tuesday, Wednesday, Thursday, Friday, Saturday, and Sunday.

The other options are incorrect because:

  • After Monday is Tuesday.
  • During Monday is not a meaningful phrase.
  • Before Monday is Sunday.