四边形ABCD中，AB=3、BC=4、CD=13、DA=12、∠CBA=90°，那么它的面积为（ ）
A．32
B．36
C．39
D．42
如图所示：连接AC，
∵AB=3，BC=4，∠CBA=90°，
∴AC=
=AB2+BC2
=5，32+42
∵△ACD中，52+122=132，即AC2+AD2=AC2，
∴△ACD是直角三角形，
∴S四边形ABCD=
S△ABC+S△ACD=1 2
×3×4+1 2
×5×12=36．1 2
故选B．
| 完形填空。从每题A、B、C中选出可填入空白处的最佳答案。 | |||
| My name is John. I am a 1 in a shop. I usually 2 at seven. Then I 3 breakfast. I often have an egg and some 4 for breakfast. My wife often has some milk, too. I go 5 at 8:00 a.m, I am 6 in the shop. There is 7 work to do. Lunch is 8 12:00 a.m, work begins at half 9 one in the afternoon. I finish my work at a quarter to six, and come back home at six. I have supper at home. 10 supper, I watch TV. I go to bed at about eleven o'clock. | |||
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