請問下面這道題選哪個答案呢?請詳解

題目：

請問下面這道題選哪個答案呢?請詳解
「I was touched by the children here who called me 'Grandpa Wen' because that's ___ the Chinese children call me at home," said Wen Jiabao in India．
A．how B．what C．why D．when．

解答：

應該選B,劃線部分替代的是call me 後面的賓語,縱觀四個選項,只有what做代詞能當賓語.