1. Given $A=\{a, b, c \mid, B=\{-1,0,1\}$, the mapping $f$ from $A$ to $B$ satisfies $J(a)=$ $f(b)+f(c)$, then the number of mappings $f$ is ( ).
A. 2
B. 4
C. 5
D. 7
1. D

According to the definition of mapping, there are a total of 7 mappings $f$ that satisfy $f(a)=f(b)+f(c)$:
$$
\begin{array}{l}
f(a)=f(b)=f(c)=0 ; \\
f(a)=f(c)=-1, f(b)=0 ; \\
f(a)=f(c)=1, f(b)=0 ; \\
f(a)=f(b)=1, f(c)=0 ; \\
f(a)=f(b)=-1, f(c)=0 ; \\
f(a)=0, f(b)=1, f(c)=-1 ; \\
f(a)=0, f(b)=-1, f(c)=1 .
\end{array}
$$