题目

PART TWO  LANGUAGE KNOWLEDGE SECTION  A Directions: Beneath each of the following sentences there are 4 choices marked A,B,C and D. Choose the one answer that best completes the sentence(25%). 21. Perseverance is a kind of quality and that is ______ it takes to learn English well.      A. what                               B. that                          C. which                      D. How一种观赏植物的花色由两对等位基因控制，且两对等位基因位于两对同源染 色体上。纯合的蓝色品种与纯合的鲜红色品种杂交，F1为蓝色，F1自交，F2为9蓝：6紫：1鲜红。若将F1测交，则后代表现型及其比例是 A．蓝：紫：鲜红  9：6：1     B．蓝：紫：鲜红   1：2：1  C．蓝：紫：鲜红  1：1：1     D．紫：蓝 3：1