若|x+y-5|+(xy-6)2=0,则x2+y2的值为[ ]
A.13
B.26
C.28
D.37
答案:A
Maria would not go to the party, as she had no fine dress, no jewelry _____.
A.to show
B.shown
C.showing off
D.to show off
通过物理、化学和生物的作用,微量有机污染物进入水体后能降解和消失,说明该水体有()。
A.氧化能力
B.还原能力
C.自净能力
D.清除能力
E.分解能力