预习yù xí
to prepare a lesson上shàng
on, on top, upon, first (of multiple parts)专家zhuān jiā
expert, specialist专心zhuān xīn
to concentrate, absorption业余yè yú
spare time, amateur, extra-curricular中心zhōng xīn
center, heart, core主席zhǔ xí
chairperson, premier, chairman主持zhǔ chí
to take charge of, to manage or direct从事cóng shì
to go for, to engage in, to undertake