当混凝土试件送检不合格后，如何处理：到施工现场____、或者回弹;如果再不合格，返工处理

A. very friendly
B. very useful
C. very thoughtful.
D. very wealthy

A. most serious disappointments
B. most significant advances
C. most abrupt declines
D. most crucial situations

A. on top of
B. next to
C. in spite of
D. with respect to