什么是宾语从句什么是复合句

Mary said,'Why didn't you call me yesterday?'(改成宾语从句)
Mary asked me why I hadn't called her the day before.
I happend to know some ways to kill mice.(改为复合句)
I happend to know some ways in which we could kill mice.
复合句就是原先简单句中的主语、宾语、表语、定语、状语、同位语等由原先的单词或者短语改为从句之后形成的“大”句子叫复合句.充当各个成分的小句子叫分句或者从句,都由连接词（或关系词语）引导,从句之外的部分叫主句（也就是原先简单句的骨干部分）.
宾语从句就是用从句来作宾语.
Have you understood?