apt to

Iron tools are apt to rust if they are left outside in the damp night air.

(Chinese) 铁制工具如果留在外面潮湿的夜间空气中，往往会生锈。

Young children are apt to be shy when meeting large groups of strangers.

(Chinese) 幼儿在面对一大群陌生人时往往会害羞。