We have a big playground in our school .We all like to 1 games 2 after school .It's Friday .We have only two classes 3 the afternoon . 4 school is over（结束的）,a lot of students go to the playground quickly.  The boys of Grade Two often 5 soccer. The girls like 6 them playing .Soccer is their favorite sport . Their teacher Mr Li also 7 football. Li Ming , Li Lei and Wei Fang are students of Grade One .They sometimes play 8 the students of Class Two. It’s half past five 9 . It's time 10dinner . My father is waiting for me at the school gate .

如图，直线c与直线a、b相交，且a//b，则下列结论：(1)∠1=∠2；(2)∠1=∠3；(3)∠3=∠2中正确的个数为（    ）

下面的几种现象中，属于可遗传变异的是（    ）