背书人甲将一张500万元的汇票分别背书转让给乙和丙各250万元，下列有关该背书效力的表述中，正确的是()

A.背书有效

B.背书无效

C.背书转让给乙250万元无效，转让给丙250万元有效

D.背书转让给乙250万元有效，转让给丙250万元无效

With the final examination ______, we are busy going over what we’ve learnt this term.

A．is approaching

B．has approached

C．approached

D．approaching