My mind wasn’t on what he was saying 和 I’m afraid I had missed half of it 都是宾语从句的用法
I’m afraid I had missed half of it 省略 that
I’m afraid （that）I had missed half of it 这里是that引导的宾语从句
My mind wasn’t on what he was saying 这里what引导宾语从句
My mind wasn’t on what he was saying so I’m afraid I had missed half of it.可以这样分开看My mind wasn’t on what he was saying
so I’m afraid I had missed half of it