(2) If the modulus of the complex number $(a+2 \mathrm{i})(1+\mathrm{i})$ is 4, then the value of the real number $a$ is $(\quad)$.
(A) 2
(B) $2 \sqrt{2}$
(C) $\pm 2$
(D) $\pm 2 \sqrt{2}$
(2) C Hint: From the problem, we have
$$
\sqrt{2} \cdot \sqrt{a^{2}+4}=4 \Rightarrow a= \pm 2 .
$$