1. Let $P$ be the set of prime numbers, and $H$ be the set of composite numbers. Define $I(n)=\left\{\begin{array}{ll}1, & n \in P ; \\ 0, & n \in H .\end{array}\right.$
Below are three propositions:
(1) For any $x 、 y \in P$, we have $I(x+y)=0$;
(2) For any $x 、 y \in H$, we have $I(x+y)=0$;
(3) For $x \in P, y \in H$, we have $I(x+y)=0$. Among these, the number of true propositions is ( ).
(A) 0
(B) 1
(C) 2
(D) 3
$-1 . A$
If $x=2, y=5$, then $x+y=7$, so
$$
I(x+y)=I(7)=1 \neq 0,
$$

thus proposition (1) is not true;
If $x=4, y=9$, then $x+y=13$, so
$$
I(x+y)=I(13)=1 \neq 0,
$$

thus proposition (2) is not true;
If $x=3, y=8$, then $x+y=11$, so
$$
I(x+y)=I(11)=1 \neq 0,
$$

thus proposition (3) is not true.
In summary, there are 0 true propositions.