题目

AA×aa杂交的F1自体受精直到第a代，每一新的世代会怎样（    ） A．杂合子的百分数减少              B．杂合子的百分数不变 C．杂合子增加                      D．基因型的比例（3︰1）不变 答案：A阅读下面一则学校海报，选择正确答案。SCHOOL EVENTSOPEN DAY（开放日）：AUGUST 16th, 2012 9:00 ~ 12:00 a.m.All parents can come to our school, have a cup of coffee, and meet our teachers and other parents.Parents can go to the classrooms of 12 ~ 15 years old, have a talk with the principal (校长), have a look at the clubs and ask any questions.All requirements（要求）for a happy school are welcome.Lunchtime: 11:30 ~ 12:00 a.m.Please go to Room 305 for lunch.All parents are welcome. Please contact (联系) us.Contact: Melodie Lezar, the principalTEL: 021- 4615998E-mail: disapark@ telkoms.a.netSchool: Goodwin Middle School（1）When is the school's Open Day?A.July 16th.B.August 16th. C.In August.D.11:30 ~ 12:00 a. m.（2）The parents can be in the school for ____________ hours.（ ）A.oneB.twoC.threeD.four（3）The parents can have a look at ____________ on the Open Day.（ ）A.other parentsB.the teachers' classroomC.Room 305D.classrooms and clubs（4）Where do parents have lunch on the Open Day?（ ）A.In a park.B.Room 305.C.At home.D.In the classroom.（5）What's the name of the school? ____________.A.Goodwin Middle SchoolB.Melodie LezarC.disapark@ telkoms. a. netD.021- 461599821