How did muhammad of mecca come to successfully spread his new religion islam across these arabian peninsula

Well, I already know this since I am Muslim and in the religion he is in Islam. Here's your answer.

He sent messages to people to tell them about Islam and shared the message to people.

The answer is C: "It helped to unify much of the Arabian peninsula under Islam"

john maynard keynes developed new economic theories in response to the stock market crash of 1929. great depression of the 1930s. first and second world wars. economic boom of the 1950s.