[单选题]
How long would it takk zj1 bb3v/2gne y sx36a dvcp( /2evi9owxiv,. $4.0 \times 10^{20} \; atoms$ to decay to $1.0 \times 10^{19} \; atoms$ if their half-life was 14.7 years?
A. $29.4 \; years$
B. $58.8 \; years$
C. $78.2 \; years$
D. $147 \; years$
