e=ca=n+(12-n)n=23n=3⇒n=4.
答案:4.
看图填空。
This is my home. It's 1__________ of my school, and 2__________ of the park.
On Sundays, I fly kites in the 3__________ and play badminton in the 4__________.
The gym is 5__________ of the park. There is a supermarket in the 6__________ of
my 7__________. It's far 8__________ my home. My mother often goes there and buys food.
通风机入口或出口常需采用柔性短管与风管连接,柔性短管的材料一般选用()
A、帆布
B、玻纤布
C、橡胶
D、一般布料