1. Given the function $f(x)=a \ln x+x^{2}$ has an extremum at $x=1$, then the value of the real number $a$ is
A. -2
B. -1
C. 1
D. 2
Solve:
$f^{\prime}(x)=\frac{a}{x}+2 x \Rightarrow f^{\prime}(1)=a+2=0 \Rightarrow a=-2$, so choose $A$.

