50. Teachers should be _____ with their students but should not be _____ on them.

A．hard; strict

B．strict; hard

C．hardly; strictly

D．strictly; hardly

从汉至唐朝，在今壮族地区出现了一些“雄于乡曲”的大姓，如番禹的目氏，高凉，合浦的冼氏，钦州的宁氏等被称为（）

A.百越大姓

B.雄于大姓

C.高凉大姓

D.壮族大姓