Which of the Following Represents an Express Condition

Which of the following represents an express condition?

A) Nora will babysit her sister's children only until the original nanny returns from vacation.
B) Beth can buy a car only when she has gathered enough funds.
C) Ruth promises to drop the mail at her mother's place provided there is no traffic.
D) If Anna gets support from her family, she will pursue further studies.
E) It is implied that when Jack promises to mow the front yard, he will mow the back yard as well.