Mother dropped the glass ________ she was standing up from her s

Mother dropped the glass ________ she was standing up from her seat.
A、and
B、but
C、so
D、as
【正确答案】：D
【题目解析】：考察连词，as 在这里表达“ 在……时”的意思。原意：母亲从座位上站起来时，杯子掉了。