A:has delivered
B:has been delivering
C:will be delivering
D:deliver
My mother called and asked me if I had _______ the birthday gift from her.
①努力学习科学文化知识 ②从小培养优良的品德
③积极探索,积累丰富的经验 ④放下学习,投入到祖国建设中去
对地球圈层的主要特点,描述正确的是( )