问题补充：
---Bear in mind that you won be able to cancel the contract youve signed.
--- I .
A. unless; do
B. since; will
C. once; will
D. after; have
答案：
A. unless; do
B. since; will
(答案→)C. once; will
D. after; have
解析：句意: ---- 要一定牢记,一旦签了合同, 你就不能撕毁它。---- 我会的。
once 意思为 “一旦；一……就”,对于祈使句的回答要用wil。
