已知：Rt△ABC中，∠ACB=90°，CA=3，CB=4，设P，Q分别为AB边，CB边上的动点，它们同时分别从A，C出发，以每秒1个单位长度的速度向终点B运动，设P，Q运动的时间为t秒．
—As we know it's difficult to live in a foreign country.
—________ if you can't understand the language there.
下列说法中正确的是 ( ).
