Join vs. assemble

[artic]

Test No. incompl/inter-16 "Letter Writing", question 5

When you are going to write an important letter like that, it is absolutely essential that you ......... all the facts first.

(a) connect
(b) join
(c) deliver
(d) assemble

Test No. incompl/inter-16 "Letter Writing", answer 5

When you are going to write an important letter like that, it is absolutely essential that you assemble all the facts first.

Correct answer: (d) assemble

Your answer was: incorrect
When you are going to write an important letter like that, it is absolutely essential that you join all the facts first.
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Why word :join: doesn't fit in here?

[Torsten]

Because you can join an organization (a party, the army, a group of people), that means you become a member of that organization.
To assemble facts means to organize and arrange them and that's clearly what the author wants to say in the sentence you are referring to.
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Test Of English for International Communication
TOEIC Preparation & TOEIC Vocabulary

[Thuytu9]

Thanks so much for your clear explanation.