Zhai Zhigang is known          the world          a hero        his walk in space.

A．as, as, for

B．to, as, for

C．to, as, on

D．in, for, as

浆砌片石灰缝应做到灰浆饱满、密实，并应避免出现干缝、（）及灰缝过大现象。