【单选题】The description of a language at some point in history is called a______study.
【单选题】The description of a language as it changes through time is a______ study.
【简答题】按重量计算含磷为16%的铜母合金答案:28480000
【单选题】Based on the description of a lahar deposit, how do clasts and matrix particles differ in size?
A.
Any clast is larger than the largest matrix particle.
B.
Any clast is smaller than the smallest matrix particle.
C.
Some, but not all, clasts are smaller than the largest matrix particle.
D.
Some, but not all, matrix particles are larger than the smallest clast.
【判断题】The description of a language at some point of time in history is a diachronic study ,but the description of language as it changes though time is a synchronic
【单选题】铝热反应常用于冶炼或焊接金属,其反应原理可表示为3CuO+2Al?3Cu+Al 2 O 3 .现将一定量铝粉和氧化铜混合加热,充分反应后停止加热.为了检验氧化铜是否有剩余,取少量反应后的固体,加入足量稀硫酸,反应后将铁片插入上层溶液中.下列叙述的现象,能够说明氧化铜有剩余的是( )
【简答题】The description of a language at some point of the time in history is a _________ study ; the description of a language as it changes through time is a _________ study.
【单选题】将一定量铝粉和氧化铜混合加热,反应的化学方程式为 3CuO+2Al 3Cu+A1 2 O 3 .反应结束后,为了检验氧化铜是否完全反应,取少量反应后的固体,加入足量稀硫酸,充分反应后,将铁片插入溶液中。下列叙述的现象中,能说明氧化铜没有完全反应的是