鉴别眼性斜颈与外科斜颈的简便方法是（）

A.同视机检查

B.遮盖一眼

C.散瞳检查

D.斜视角检查

E.胸锁乳突肌检查

— _________, this math problem seemed quite simple to me, but when I tried to work it out, I just couldn’t.

— There are always things like this, I think.

A．On one hand

B．In my opinion

C．At first sight

D．On its own