All the students _______ very hard over the last three years.
A:works
B:has worked
C:have worked
D:worked
—No. For example, he said he would show me around his school, and _______ .
附: K2=n(ad−bc)2(a+b)(c+d)(a+c)(b+d)
P(K2≥k0)
0.100
0.050
0.010
0.001
k0
2.706
3.841
6.635
10.828
他们是中国的照片。