Gaokao Math Practice Question
设集合 $A=\left\{x \mid x^{2}-4 \leq 0\right\}, B=\{x \mid 2 x+a \leq 0\}$, 且 $A \cap B=\{x \mid-2 \leq x \leq 1\}$, 则 $a=(\qquad)$
- A.$-4$
- B.$-2$
- C.2
- D.4
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