Hu Jintao on Tuesday________ resuming（继续）cross-strait talks on the basis of the "1992 Consensus" as

early as possible, to resolve problems in a practical manner.

A．called on

B．called in

C．called for

D．called at

井壁不稳定是指钻井和完井过程中的井壁坍塌、缩径和地层压裂三种基本类型。