—He's already back to the USA, __________?
—_________.He is on a business trip in Suzhou.
A:isn't he; Yes
B:hasn't he; No
C:hasn't he; Yes
D:isn't he; No
—Hi, Mum. This is Miss Li.
—________
张华和同学到游子山参加社会实践活动,拾到一些不规则小石块,他们很想知道这种小石块是什么材料做成的,就把它们带回学校利用天平和量筒来测定这种小石块的密度。
Is it ____? Yes, it is hard.