Question

. After I went on a diet, my pants were too ______
A) loosen
B) lose
C) loss
D) loose
E) losed

Answer 1

 After I went on a diet, my pants were too 
loose

Answer 2

After I went on a diet, my pants were too "loose"

loosen is incorrect since it is in Infinitive tense (is incorrect)     Х
lose means unable to find(is incorrect)                                        Х
loss means the process of losing something (is incorrect)        Х
losed it is a past tense    (is incorrect)                                         Х

Hence the correct word is loose,which is in present continuos tense.