The world’s nations must cooperate. one nation cannot solve the world’s problems by itself. which is the best way to combine the sentences using a semicolon? the world’s nations must cooperate; for one nation cannot solve the world’s problems by itself. the world’s nations must cooperate; one nation cannot solve the world’s problems by itself. the world’s nations must cooperate; one nation cannot solve the world’s problems by itself.

Correct answer # 2: The world's nations must cooperate; one nation cannot solve the world's problems by itself.

When you connect two related independent clauses or sentences you use a semicolon. Both sentences should be completed grammarly writtend and with a connection. Make sure you do not write a capital letter after the semicolon, unless it is a proper name.

Answer # 3 is incorrect as there is a capitalized word

Answer # 1 it is incorrect to use "for" as the sentence is grammarly completed

greet them:

buenas noches.

that is considered night time which is when "good night" is used.

the krebs cycle and electron transport occur in the mitochondria, though other than that i would need to know more information.