Chọn mệnh đề đúng:

A.\[\smallint f'\left( x \right)dx = f\left( x \right) + C\]

B. \[\smallint f\left( x \right)dx = f'\left( x \right) + C\]

C. \[\smallint f'\left( x \right)dx = f''\left( x \right) + C\]

D. \[\smallint f\left( x \right)dx = f''\left( x \right) + C\]