(1) Let the set $P=\{(x, y) \mid y=k\}, Q=\left\{(x, y) \mid y=a^{x}+1, a>0\right.$ and $a \neq 1\}$, it is known that $P \cap Q$ has only one subset, then the range of values for $k$ is ( ).
(A) $(-\infty, 1)$
(B) $(-\infty,+1]$
(C) $(1,+\infty)$
(D) $(-\infty,+\infty)$
(1) $P \cap Q$ has only one subset, which means $P \cap Q$ is an empty set. From the graphical analysis, when $k \leqslant 1$, the line $y=k$ has no intersection points with the curve $y=a^{x}+1$. Therefore, the correct choice is B.