Question

it does sound tempting为什么不加s

Answer 1

由于前面有does,后面的动词sound就不再加s了.这里does的作用是表示强调,译成汉语是：那听起来确实吸引人.

英语里的强调有时可以通过加助动词do/does、did来实现.例如：

I did go to the school this morning.（我上午确实上学去了【母亲怀疑他没去上学】）.

She did ask me to tell you that.(她确实让我告诉你这个【对方怀疑没这回事儿】).