题目

用方框中所给短语的适当形式填空 take a trip；look after；turn down；help out；hear from 【1】I have to ____________with my son's homework tonight.【2】The Smiths plan to _______________to China next month.【3】We are looking forward to ____________ you soon.【4】His wife stayed at home and ______________ the children.【5】David ______________the job offer because of the low salary.已知450℃时，反应H2(g)+I2(g) 2HI(g)的K=50，由此推测在450℃时，反应2HI(g) H2(g)+I2(g)的化学平衡常数为（ ）A.50B.0.02C.100D.无法确定