1. [单选题]裸子植物的胚乳是( )。
A. 配子体世代，核相为n
B. 配子体世代，核相为3n
C. 孢子体世代，核相为2n
D. 孢子体世代，核相为3n
2. [单选题]
B． writing C． drawing D． exercising
A. cleaningB． writing
B. drawing
C. exercising
3. [单选题]下列蕨类中柱类型中，最原始的中柱类型是( )。
A. 原生中柱
B. 管状中柱
C. 网状中柱
D. 多环中柱
4. [单选题]After seeing the good students’ designs，some students _________.
A. 1oved their own designs more
B. thought they had a fair chance
C. put their own designs in a comer
D. thought they would not win the prize
5. [单选题]根系有两种类型，直根系(axial root system)是由主根发育而来，须根系是由侧根发育而来。( )
A. 正确
B. 错误
