单项选择题

砌筑砂浆试配时用机械搅拌,搅拌时间应自开始加水时算起,预拌砌筑砂浆和掺有粉煤灰、外加剂、保水增稠材料等的砂浆搅拌时间不得少于()

A.100S
B.120S
C.150S
D.180S