We had to ______ our visit to the pyramids because we didn’t have enough time to see them before we left Egypt.

A．prohibit

B．postpone

C．predict

D．preserve

硅结节境界清楚，直径2～5mm，呈圆形或椭圆形。灰白色、质硬，触之有砂样感；结节中央往往没有血管。