1、They all (agree,同意) that old people were cleverer than young people. 他们都同意老年人比年轻人要聪明些. 2、That's (why,为什么) I'm as strong as before. 那就是我为什么像以前一样结实的原因.
对了解释一下,2句前面有一段话:When i was young, i couldn't move the stone.i wasn't strong enough.Now i'm old and when i try ro move it. i still can't. that's (w )i'm as strong as before.