I just wonder       that makes you so excited．

A.why it does

B.what he does

C.how it is

D.what it is

答案及解析： D

解析：

考查宾语从句，此题的宾语从句为强调句型，后应用陈述句语序，句意：我只是想知道究竟是什么使你如此兴奋。所以选D。