单项选择题

GB/T50080-2016,扩展度试验及扩展度经时损失试验,自()时,静置()后将混凝土拌合物试样全部倒入搅拌机内,搅拌即进行扩展度试验。

A.30min;60s
B.30min;20s
C.60min;60s
D.60min;20s