[单选题]
A 4.0-N force acts f kso/,3bhw f5z6r l-ilqmthfoyc32 6 *or 3.0 s on an object. The force suddenly increases to 15 N and acts for one more second. What impulse was imparted by these forces to tth* yqfo 32c6mhe object?
A. $12 \; N \cdot s$
B. $15 \; N \cdot s$
C. $19 \; N \cdot s$
D. $27 \; N \cdot s$
