填入下面一段文字横线处的语句，最恰当的一句是（ ）辣，我们都不陌生，很多人无辣不欢甚至吃辣上瘾，这是因为辣椒素等辣味物质刺激舌头、口腔的神经末梢时，会在大脑中形成类似灼烧的感觉，机体就反射性地出现心跳加速、唾液及汗液分泌增多等现象， ，内啡肽又促进多巴胺的分泌，多巴胺能在短时间内令人高度兴奋，带来“辣椒素快感”，慢慢地我们吃辣就上瘾了。

Are you happy with this laboratory? — Not a little. We can’t have ________.

In students’eyes．a good teacher should have many good virtues，but ，heor she should be knowledgeable

This is the place ________________the foreign guests are going to visit.

She was so _____ in her job that she didn’t hear anybody knocking at the door.