46. What is the main point of this passage?
(A)Understanding professors' questions is important.
(B) Behaving oneself is important.
(C) Participation in class is important.
(D) Being polite in college is important.

42. (A)but (B)if (C)when (D)because

43. (A)and (B)if (C)but (D)or

44. (A)make (B)have (C)do (D)take

45. (A)call (B)called (C)calling (D)to call

47. How long does a professor usually wait for the student's answer? (A)Less than 10 seconds. (B) Between 30 to 60 seconds. (C) About two minutes. (D) Long enough for the student to come up with good answers.

48. What is Not a professor's expectation of his or her students? (A) Attending class. (B) Being polite in group discussions. (C) Sharing personal experience. (D) Expressing agreements with everything

49. In group discussions, what behavior do professors consider acceptable? (A)Interruption (B) Quietness (C) Rudeness (D) Talking on the cell phone

50. Which following statement about college students is true? (A)They are free to skip classes. (B) They are usually punished for talking in class. (C) Their professors get angry if the students do not know the answers. (D) Their professors encourage them to express their opinions.

1.生物膜将真核细胞分隔成不同的区室，使得细胞内能够同时进行多种化学反应，而不会相互干扰。下列叙述正确的是  (A).细胞核是mRNA合成和加工的场所         (B).高尔基体是肽链合成和加工的场所   (C).线粒体将葡萄糖氧化分解成CO2和H2O     (D).溶酶体合成和分泌多种酸性水解酶

2细胞代谢受酶的调节和控制。下列叙述正确的是   (A).激素都是通过影响靶细胞内酶活性来调节细胞代谢  (B).代谢的终产物可反馈调节相关酶活性，进而调节代谢速率   (C).同一个体各种体细胞酶的种类相同、数量不同，代谢不同   (D).对于一个细胞来说，酶的种类和数量不会发生变化