在这句Let us play volleyball,that sounds good中!为什么SOUND要加S呢?我要好

在这句Let us play volleyball,that sounds good中!为什么SOUND要加S呢?我要好 That sounds good.这里的sound为什么要加s? That sounds good的sound为什么要加s?直接sound不好了 let us play volleyball.------- that sounds b__ what is this sound interesting 为何不加,That sounds good 为何要加s,如果用that sounds let us play volleyball.that is a good That sounds good中的sounds为什么要加s That sounds good.这句话sound后面为什么要+s?什么情况下sound+s?12.24月考, that sounds good 这里sound为啥加s Let‘s play football.That’s sounds good.改错 Nither of us plays volleyball well.中play为什么要加s lat's play volleyball,_that sounds good这句话错在哪