【单选题】人体健康离不开化学。下列叙述错误的是( )
A.
海产品、瘦肉、肝脏含有丰富的人体所需的锌元素
D.
人体氟过量会引起氟骨病,氟元素缺乏会导致龋齿
【判断题】Simple machines allow work to be done in an easier way
【简答题】Today, bicycles are elegantly machines that are common around the world. Many people ride bicycles for recreation, whereas others use them as a means of transportation. The first bicycle was in...
【多选题】在中国金融期货交易所上市交易的股指期货品种有( )。
【多选题】在中国金融期货交易所上市交易的股指期货品种有( )。
【单选题】国际邮件按()可分为普通邮件、全球优先函件和特快专递邮件。
【简答题】国际邮件按处理时限划分,可分为()、()、()等几种。并在外表面注有专门标志。
【判断题】There are a lot of simple machines.
【判断题】Complicated machines consist of simple machines.
【单选题】According to the text, simple machines can do the following but
A.
allow energy to be transferred from one place to another
B.
change the distance and speed of a moving object
C.
perform the task automatically