Read this student rough draft.

[1] suburban neighborhoods offer safety, comfort, and a sense of community. [2] neighbors get to know one another through frequent curb-side encounters. [3] neighbors often rely on one another. [4] this reliance builds friendships.

how could sentences 3 and 4 be combined to form a complex sentence?

neighbors rely on one another and form friendships.
there is reliance among neighbors, and there are friendships.
relying on one another leads to friendships.
once neighbors rely on one another, friendships are formed.