将含Ba²⁺的试剂滴入下列离子的溶液中，有白色沉淀产生的是（　　）

A．NO₃^-

B．SO₄^2-

C．OH^-

D．Cl^-

The number of people invited to the party       200 but a number of them         ___absent for different reasons.

A．were ; was

B．was ; were

C．was ; was

D．were ; were