题干

下列有关植物组织培养的叙述,正确的是( ) 

A:愈伤组织是一团有特定结构和功能的薄壁细胞

B:二倍体植株的花粉经脱分化与再分化后得到稳定遗传的植株

C:用人工薄膜将胚状体、愈伤组织等分别包装可制成人工种子

D:不同阶段的培养基中细胞分裂素和生长素的比例不同

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D

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     I was very disappointed not to be able to go to the jazz concert last Friday. The advertisement in the paper said that you could buy tickets at the theatre box in Richland Hills any day between 10:00 and 4:00. Since I work from 9:00 to 5:30, the only time I could go to the theatre was during my 45-minute lunch break.

    Unfortunately, the theatre is on theother side of the town, and the bus service between my office and Richland Hills is not very good. Butif you are lucky, you can make the round trip in 45 minutes. Last Monday, Istood at the bus stop for 15 minutes waiting for the bus, By the time I saw onecome around the corner, there was not enough time left to make the trip.

     So I gave up and went back to the office. The same thing happened on Tuesday, and again next day. On Thursday, my luck changed. I got on a bus right away and arrived at the theatre in exactly 20 minutes. When I got there, however, I found along line of people at the box office, I heard one man say he had been waitingin line for over an hour. Realizing I would not have enough timeto wait in line. I caught the next bus and headed back across the town.

    By Friday I realized my only hope was tomake the trip by taxi, it was expensive, but I felt it would be worth it tohear the concert. The trip by taxi only took 10 minutes, but felt like an hour to me. When I got to the theatre, I was relieved to see that nobody was waiting in line. The reason, however, I quickly discovered, was that they had already sold all the tickets.