1 + 2 + 3 + ... + 12 = ?  Choose the correct choice from the following answers
A) 76	B) 68	C) 78	D) 66	E) 67
1+2+3+⋯+n=∑n=n(n+1)/2   1+2+3+⋯+12=n(n+1)/2=(12(12+1))/2=(12×13)/2=6×13=78   Answer is 78
<result>C</result>
1 + 2 + 3 + ... + 12 = ?