1.Medical researchers are painfully aware that there are many problems __________________(他们至今还没有答案).
2.___________________________(大多数父母所关心的) is providing the best education possible for their children.
3.You’d better take a sweater with you ________________________________(以防天气变冷).
4.Through the project, many people have received training and _____________(决定自己创业).
5.The anti-virus agent was not known ___________________ (直到一名医生偶然发现了它).
参考答案：
1. that they haven’t found answers to
解析：知识点是定语从句，注意answers后面的介词to不要弄丢。
2. What most parents are concerned about
解析：知识点是主语从句。
3. in case it (should) turn(s) cold
解析：知识点是特殊虚拟语气in case用法，should+动词原形，should可以省略。
4. decided to start their own business
解析：知识点是词组decide to do sth.，注意时态。
5. until it was accidentally found by a doctor
解析：知识点是词组not … until, 时态。