— Can you explain ____ you have been late for school several times this term?
— Sorry, but it is the first time that I have been late this week.
| A．why it is that | B．how it is that |
| C．why is it that | D．how is it that |
The Bakers intend to buy a house but _____ must be within their power.
| A．they | B．one | C．it | D．which |
Fully ______in preparing teaching assignment at school，she no longer has much time to enjoy the various activities as usual.
| A．occupy | B．occupying |
| C．occupied | D．to occupy |
---Where is your report of this month？
---Oh sorry，I______ to email to you.
| A．forget | B．have forgotten |
| C．forgot | D．was forgetting |
She is always the first staff to go to the office and the last to leave，______ I guess is why she is promoted so quickly.
| A．who | B．which | C．that | D．what |
EBOLA（埃博拉） is said_______ another big health challenge to our humans over the past several months .
| A．becoming | B．to become |
| C．having become | D．to have become |