it is __ to swim in the river in summer.sure it is,look at the sign.it says no swimming

问题描述:

it is __ to swim in the river in summer.sure it is,look at the sign.it says no swimming
funny
exciting
dangerous
diffcult

选 dangerous 危险的.
后文说了 no swimming,禁止游泳.所以看出来是危险的.