—Have you been working in N0.5 Middle School since you graduated from college?

~No, I _______ in the countryside for 3 years.

A．have taught

B．had taught

C．have been teaching

D．taught

影响砌体抗压强度的主要因素是（）。

A．块体和砂浆的强度

B．块体的规整程度和尺寸

C．砂浆的变形与和易性

D．水平灰缝砂浆饱满度