29. Tossing a fair coin 10 times, the probability of getting exactly three tails is ( ).
(A) $\frac{15}{128}$
(B) $\frac{3}{10}$
(C) $\frac{21}{100}$
(J) $\frac{1}{8}$
$(\mathrm{E}) *$
29. (A).

Due to tossing a coin 10 times, there are $2^{10}$ possible outcomes, among which there are $\mathrm{C}_{10}^{3}$ outcomes with exactly 3 tails. Thus, the probability is
$$
\frac{C_{10}^{3}}{2^{10}}=\frac{10 \cdot 9 \cdot 8}{6 \cdot 2^{10}}=\frac{15}{128} .
$$