黄明胶属于() ["A.发胶类","B.角胶类","C.甲胶类","D.骨胶类","E.皮胶类"]
空斗砖墙砌式具有用料省,自重轻的特点,通常可适用于()的房屋。 ["3层以下","4~6层","7~9层","10层以上"]
黄体酮与亚硝酸基铁氰化钠反应,在一定条件下生成蓝紫色,是因为() ["黄体酮含有△-3-酮基","黄体酮含有酚羟基","黄体酮含有α-醇酮基","黄体酮含有羰基","黄体酮含有甲酮基"]
双下肢中枢性瘫痪() ["高颈段脊髓病变","脊髓颈膨大病变","胸段脊髓病变","脊髓腰膨大病变","骶段脊髓病变"]
患病后不按照医嘱服药的行为属于() ["日常危害健康行为","致病性行为模式","不良疾病行为","违规行为","预警行为"]
简述我国森林资源开发利用中存在的问题。