y=sin（-2x+π/6）= -sin(2x-π/6)
2x-π/6∈(2kπ-π/2,2kπ+π/2）时单调减
所以单调减区间：(kπ-π/6,kπ+π/3）,其中k∈ZA：[-π/6+2kπ，π/3+2kπ]B：[π/6+2kπ，5π/6+2kπ]C：[-π/6+kπ，π/3+kπ]D：π/6+kπ，5π/6+kπ