[单选题]
A 4.0-N force acts for 3.0 so5 n5mpqb834vwyb( w s on an object. The force suddenly increases to 1zk :az+c+; sqz5 N and acts for one more second. What impulse was;k ++czsqzz:a imparted by these forces to the object?
A. $12 \; N \cdot s$
B. $15 \; N \cdot s$
C. $19 \; N \cdot s$
D. $27 \; N \cdot s$
