What is the function of transition words?

a$.$ Make the reader think that the reader is credible because they use language that connects ideas to one another.

b$.$ Introduce and inform the reader of a paragraph's purpose.

c$.$ Inform the reader that they can skim the following paragraph while retaining the main point of its content.

d$.$ Guide the readers from paragraph to paragraph and point to point within a paragraph in ways that orients readers to the writer's logic.