Therefore is an adverb it shows a consequence, a result

Negation is a logical connective. In philosophy, it means that it takes truth to a falsehood, and falsehood to a truth.

Ligaments connect bones to other bones, and tendons connect muscles to bones; since connection is their function, it is logical that they should be made of connective tissue, don't you think?

The logical connective "or" is called the disjunction of the statements R and S in the statement "R or S."

No, a preposition is a part of speech that shows the relationship between a noun or pronoun and other words in a sentence. A connective, on the other hand, is a word or phrase that links different parts of a sentence or text together to show logical relationships.