英语动词用法问题!

题目

英语动词用法问题!
Schardt said the lead and vitamin A findings are worrisome because vitamins are generally taken every day,potentially building up to toxic levels and leading to problems down the line.In particular,he noted,women with high levels of lead in their bodies who become pregnant could pass on problems to a fetus.
最后面得become的动词用法是什么?是一般的谓语动词吗?感觉这里好像好用过去时吧?高手们给给帮主,

答案

"become"做动词,用一般现在时表事实结果,不必用过去时.