It’s clever _____ her to work out _____ many difficult math problems.

24．This is an exciting area of study，_______new applications are being discoveredalmost daily．

your book, and do your work first. You may read it later.

____ pay Tom a visit, but I am notsure whether I will have time this Sunday.

It is wise of you towell trained workers for untrained ones in your workshop. A．substitute B．changeC．exchange D．employ