Please edit In April 12,1961, major Yuri Gagarin became the first man ever to venture
in space. He did not know for certain
beforehand that he is to be chosen
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one is a red flower, and one is the sky when the sun sets.

we need to see the paragraphs in order to answer this.

explanation:

if you’re a fan of chocolate, every occasion is right for this treat. feeling down? eat some chocolate. celebrating? eat some more. want to show your valentine how special you think your sweetheart is? offer up chocolate!   people have been enjoying chocolate as a food, drink and medicine for thousands of years. the ancient maya and aztecs called chocolate kakaw and used it as medicine. they also made chocolate offerings to their gods. chocolate comes from the cacao (kuh-kow) tree, and its scientific name reflects its history. theobroma cacao translates to “cacao, food of the gods.” these days, chocolate is not just for deities. the treat has become popular around the world.

a complex sentence consists of an independent clause and one or more dependent clauses.  

to write complex sentences, we must use subordinating conjunctions.  

all the complex sentences begin with a subordinating conjunction and when it occurs, a comma must be place at the end of the dependent clause. on the contrary, if the sentence begins with an independent clause, then no comma is used.

after  

although  

as  

because  

before  

if  

since  

when  

for example,  

after she won the competition, she became very popular.  

although my father was hurt, he continued fighting for his rights.  

as all of you got a ten, you will be able to leave early today.  

before he went to the war, he asked his parents to bless him.  

if it is cold, i won’t go out.  

since you didn’t bring the homework, you will get low grades.  

when it is hot in the town, everyone goes to the beach.