11. E.

Let the number of campers who can only sing be $x$, the number of campers who can only dance be $y$, the number of campers who can only perform be $z$, the number of campers who can sing and dance be $a$, the number of campers who can sing and perform be $b$, and the number of campers who can dance and perform be $c$.
$$
\begin{array}{l}
\text { Then }\left\{\begin{array}{l}
x+y+z+a+b+c=100, \\
y+z+c=42, \\
z+x+b=65, \\
x+y+a=29
\end{array}\right. \\
\Rightarrow a+b+c \\
=2(x+y+z+a+b+c)-(y+z+c)- \\
\quad(z+x+b)-(x+y+a) \\
=64 .
\end{array}
$$
11. In a certain summer camp, 100 campers each have at least one of the following talents: singing, dancing, or performing. Some have more than one talent, but no one has all three talents. If 42 campers cannot sing, 65 campers cannot dance, and 29 campers cannot perform, then the number of campers who have at least two talents is ( ).
(A) 16
(B) 25
(C) 36
(D) 49
(E) 64