问题 问答题 简答题

植物变色类病毒病怎样防治?

答案

参考答案:

①加强检疫,控制病害扩展传播;

②繁殖无毒苗木(用组培等方法);

③有毒种子用热处理进行脱毒,用70℃的高温进行干热处理;

④加强栽培管理,控制病害发生,及时拔除病株,及时清除田间杂草;

⑤防治传毒蚜虫:定期喷洒氧化乐果、马拉硫磷等杀虫剂,在修剪、切花、掰芽、嫁接等操作时要对工具及人手进行消毒处理,可用3%-5%的磷酸三钠溶液,酒精或热肥皂水反复洗涤。

阅读理解

A bag is useful and the word “bag” is useful, too. Here is an interesting phrase(短语), “to let the cat out of the bag”. In meaning it is the same as “to tell the secret(秘密)”. And there is an old interesting story about it.

  Long ago, when farmers wanted to sell chickens at the market, they would usually just throw the chickens in cloth (布) bags. But cats were cheaper than chickens at that time, so many farmers would put cats into the cloth bags but not chickens. One day, a woman asked a man for a chicken. The man gave her a cloth bag in which there was a cat.      When the man opened the cloth bag, a big black cat ran out. Not a chicken! The man’s secret was out and everyone knew it.

  Now when we say someone gives away a secret, we say “he lets the cat out of the bag”. And that is the story where the interesting phrase came from.

小题1:The underlined word “it” in the passage refers to (指的是)     .

A.the useful bag

B.the phrase

C.the cat

D.the chicken小题2:The farmers put cats but not chickens in the bags to      when they sold chickens.

A.tell the secret

B.sell the cats

C.get more money

D.keep the cats quiet小题3:Which is the best for the blank (空白处) in the passage?

A.The woman was angry to see a cat.

B.The man put a cat in the bag.

C.The man asked her to see the chicken.

D.The woman wanted to see the chicken.小题4:The writer wrote the story to tell us     .

A.the woman was smart

B.how farmers sold their cats

C.the phrase is useful

D.where the phrase came from

单项选择题