吸收式制冷机为防止管板与传热管之间的电化学腐蚀，管板应涂树脂胶加以保护。所涂树脂胶配

My brother and I have____ her birthday party.[ ]

A. been invited

B. been invited for

C. invited to

D. been invited to

生物的多样性包括         多样性、          和         多样性。

干化学法尿糖检测的是（）

A.蔗糖

B.麦芽糖

C.乳糖

D.葡萄糖

E.果糖

下列哪项不是消化性溃疡的病理特点

A．溃疡直径＜2.5 cm

B．底平坦，有灰白苔

C．溃疡圆或椭圆型边缘整齐

D．愈合一般需4～8周

E．周围黏膜紊乱，胃壁僵硬

“从学习关系SC中检索无成绩的学生学号”的SQL语句是

A．SELECT sno FROM sc WHERE grade=NULL

B．SELECT sno FROM sc WHERE grade IS

C．SELECT sno FROM sc WHERE grade IS NULL

D．SELECT sno FROM sc WHERE grade=0