英语阅读有all的选项可以选吗?B为何不可 还有75的C.D

英语阅读有all的选项可以选吗?B为何不可 还有75的C.D
Since the Internet has come into homes,the daily life has never been the same again.But the thing that worries most of us is that we can get viruses from the Internet.But can we catch viruses on our cell phones?A new study in the journey Science says yes,but the spread of such mobile software that can bring harm to our cell phones won’t reach dangerous levels until more cell phones are on the same operating system.
Computers are easily attacked by viruses because they share data,especially over the Internet.Of course,nowadays,more people are using their cell phones more and more frequently.They use them for emailing,text messaging and downloading troublesome ring tones,etc.so it is obvious that cell phone virouses are a threat ,as well.
Scientists used nameless call data from more than six million cell phone users to help model a possible outbreak.And they concluded that virouses that spread from phone to phone by Bluetooth are not much concerned,because users have to be in close physical relation for their phones to “see” one another.However,viruses that spread through multimedia messaging services can move much faster,because they can come in disguise,such as a cool tune sent by a friend.The good news is that to be effective,these viruses need their victims to all use the same operating system,which not enough of us do.Because there is no Microsoft operating system for mobile phones,yet.Thank goodness.
73.When_______,cell phone viruses can be dangerous.
A.all the cell phones work on the same operating system
B.Microsoft operating system for cell phones is created
C.users can see each other on the phone
D.Bluetooth is widely used
75.We can learn from the passage that_______.
A.it is impossible to catch viruses on our cell phones
B.cell pones are not well connected with the Internet
C.it is dangerous for people to download ring tones to cell phones
D.more than one operating system is available for cell phone users now
我的all意思是题目中出现all等太绝对的词的字眼啊 不是All of the above。

73.Abut the spread of such mobile software that can bring harm to our cell phones won’t reach dangerous levels until more cell phones are on the same operating system.这句话就是说只有当手机都在同样的...
再问： The good news is that to be effective, these viruses need their victims to all use the same operating system, which not enough of us do. Because there is no Microsoft operating system for mobile phones, yet. Thank goodness.
再答： 好消息是，要想让病毒有效果的话，受害者必须都使用同一种操作系统，而现在用户中这样的情况并不够多，因为微软还没有手机专用的操作系统。感谢上帝！ （这里面提微软，是对比电脑的现状，一方面是因为微软操作系统是著名的易携带传播病毒，另一方面则是微软系统使用的人足够多）