35 B has been repaired ( several times -> hiện tại hoàn thành ).
36 B did ( if 2: If + S1 + V2/ed, S2 + might/ would + Vinf ).
37 C balanced
38 A failed ( if 2: If + S1 + V2/ed, S2 + might/ would + Vinf ).
39 B mammals
40 B will - stand ( if 1: If + S1 + Ve/es, S2 + will+ Vinf ).
41 C had been put
42 A hasn't been done
43 D investigate
44 C reveal
45 B ocean
46 B effect
47 B furface
48 D group