[单选题]
A 4.00-kg cylinder of solid iro8ny*p0cez m rl yjs6*0n is supported by a string whila; d2ks :ju9ohe submerged in water. What is the tension in the string? (The specifics: aj;o2 u9dkh gravity of iron is 7.86.)
A. $2.50 \; N$
B. $19.6 \; N$
C. $23.7 \; N$
D. $34.2 \; N$