Open the brackets and fill in the gaps. Mind the positive or the negative forms of the imperative sentences.
1) (To switch off) ______________________________ your mobiles.
2) (To read) _____________________________________ the instructions.
3) (Not to feed) _____________________________________ the animals in the zoo.
4) (To clean) _________________________________ your teeth.
5) (Not to swim) _______________________________________ in this lake.
6) (Not to talk) _______________________________________ to strangers.