27.(indicating ancestry)(尤指人的)世系, 家系, 血脉
28.a line of sth
(series of people or events)(按时间顺序排的)一系列, 一连串
29.【数】(in geometry)线；直线
30.【数】(set of points)直线
31.【体】(on track, field, etc)界线；场线；场界
The ball was clearly over the line.这个球显然已经越线了。
32.【体】(starting line, finish line)起跑线；起点线；终点线