Question

___you happen to see Mary,would you please ask her to come here ?

A would B could C should D might

Answer 1

___you happen to see Mary,would you please ask her to come here ?
选C should
Should you happen to see Mary=If you should happen to see Mary

Answer 2

此处为虚拟语气，意思是如果你碰到Mary，能请你叫她来这里吗？
当虚拟条件句的谓语动词含有were, should, had时，if可以省略，这时条件从句要用倒装语序，即把were, should, had等词置于句首.例如：If he had taken my advice, he would not have made such a mistake.=Had he taken my advice, he would not have made such a mistake.
If he should agree to go there, we would send him there.=Should he agree to go there, we would send him there.If she were here, she would agree with us.=Were she here, she would agree with us.

Answer 3

A