在$△ABC$中，$A={90}^{°},\tan B=\frac{3}{4}$，若以$A,B$为焦点的椭圆经过点$C$，则该椭圆的离心率e=（  ）

①遥望洞庭山水翠____

②天门中断楚江开____

③碧水东流至此回____

    Do you know anything about the way of shopping in Western countries? In the West, people usually make a list before they go shopping. Most people like to go to supermarkets or big shopping malls.

    In the West, most supermarkets or malls open at 8:00 a.m. and close at 6:00 p.m. But some big supermarkets and big malls are open until 11:00 p.m. at night. When people go into a supermarket, first they should get a basket or a cart(手推车) at the entrance(入口处). Then they begin to choose things and put them into the basket or the cart. After they get everything they want, they pay the money. There are always a lot of people in the supermarket at weekends. They must wait for their turn.

    Most people go to the supermarket or the shopping mall once a week. Some people go shopping twice or three times a week.

如果△ABC的三边长a、b、c满足关系式（a+2b﹣60）²+|b﹣18|+|c﹣30|=0，则△ABC的形状是____．