you have received a letter from your english-speaking pen-friend john who writes:
i have bought, a magazine. there is an interesting horoscope. i sometimes read it. how often do you read a horoscope? do you believe in it?
why do you think people want to know their destiny?
my parents have presented me a pet.
write a letter to john.
in your letter — answer his questions — ask 3 questions about. his pet.
write 100-140 words.
remember the rules of letter writing

this would be in the imperative mood. it is a category of verb forms that are used to express orders,instructions,commands or requests.

the following key ideas correctly express the key sentence.

restate key idea: most people can learn to swim in ten short lessons.

restate key idea: the majority of water-accident victims require mouth-to-mouth breathing.

restate key idea: an empty, tightly closed gallon jug will support a tired swimmer.  

restate key idea: first aid is to prevent accidents as well as assist in rescue.

explanation: the key idea needs to have the same topic as the key sentence (drowning and safety).