根据下列句子的意思及所给汉语注释写出单词，每空一词。
____ Children must wash their clothes __________ (他们).
____ We can find the kind-hearted person __________ (到处).
____ There were two traffic __________ (事故) in the street last month.
____ His parents don't __________ (允许)him to go out alone at night.
____ Anna is a__________ (当心的) girl , she makes few mistakes in her homework.

小肠吸收来的葡萄糖送到脑部利用并将细胞产生的含氮废物转变成尿素，送至肾脏排出，整个过程中血液经过心脏和肺的次数依次是（　　）