21．— Would you mind if I take the seat next to yours?
— ___________.
A．Yes, sit down please B．No, go ahead
C．Surely, never mind D．No, you can’t take it
22．— How do you find your English teacher?
— She is always full of _____ as though she never knew tiredness.
A．strength B．force C．energy D．spirit
23．— Do you know something about Kwanzaa?
— It is _____festival celebrating the culture and history of African Americans.
A．a seven-day B．a seven-days C．a seven day D．seven days
24．_____ we choose healthy food for our main meals, we probably still need to exercise now and then.
A．Unless B．As though C．Until D．Even if