Which of the Following Uses the Doubling Method of Informal

Multiple Choice

Which of the following uses the doubling method of informal counting to solve the following:
3+4=

A) (1+1+1) + (1+1+1+1) = 7
B) (3+4) + (3+4) - (3+4) = 7
C) 3+4 = (3+3) +1 = 6+1 = 7
D) 2+2+2+1=7