.
.---Who ________ it be that is knocking at the door?
---It________ be Mother, but I’m not sure.
A. can; must B. can; may C. must; can D. may; must
.
.---Who ________ it be that is knocking at the door?
---It________ be Mother, but I’m not sure.
A. can; must B. can; may C. must; can D. may; must
B