远离犯罪，呵护青春需要我们青少年（    ）

①培养法制观念，在心中筑起法律的堤坝  ②学会控制自己的情绪，做事多考虑可能引发的后果

③辨别是非善恶，提高道德修养               ④学会树立正确的人生目标，谨慎择友

y=$\sqrt{x-3}$+$\sqrt{3-x}$+18，求3x+y的立方根．

根据短文内容，判断正误。符合短文内容，对的写正确，错的写错误。

    Ann and Lucy visit the zoo today. They see many animals there. Look, a bear is under the tree. You can see two pandas near the river. Ann and Lucy like pandas very much. There are two tigers and four leopards at the zoo. Some foxes, rabbits and squirrels are behind the rocks. Six sheep and eight goats are on the ground. They are eating grass. Ann and Lucy like all the animals at the zoo. They have a good time today.

如图所示，水平传送带以速度v₁匀速运动，小物体P、Q由通过光滑定滑轮的不可伸长的轻绳相连，t=0时刻P在传送带左端具有速度v₂，已知v₁>v₂，P与定滑轮间的绳水平。不计定滑轮质量，绳足够长，物体与传送带之间的最大静摩擦力和滑动摩擦力相等。从最初直到物体P从传送带离开的过程，以下判断正确的是（    ）

​