It is the discovery of Cao Cao's tomb, _____ was made in Anyang, Henan province, _____ has

received widespread attention.  [ ]

A. where; which    

B. where; that      

C. that; which    

D. which; that

设函数p(x)，q(x)，f(x)连续，而y₁，y₂，y₃都是方程y"+p(x)y'+q(x)y=f(x)的解，则该方程必定还有解

A．y₁+y₂-y₃．

B．y₁-y₂-y₃．

C．-y₁-y₂-y₃．

D．y₁+y₂+y₃．