10．用冷却水管降低混凝土温度，二期通水冷却应保证至少有(  )的温降。

、<span>10</span><span>～</span><span>15</span><span>℃</span>

、<span>15</span><span>～</span><span>20</span><span>℃</span><span> </span>

、<span>5</span><span>～</span><span>10</span><span>℃</span>