A:X、Y、Z三种元素最低价氢化物的沸点依次升高
B:由X、Y和氢三种元素形成的化合物中有共价键
C:物质WY2、W3X4均有熔点高、硬度大的特性
D:T元素肯定是金属元素
Bach died in 1750, but it was not until the early 19th century____ his musical gift was fully recognized.
3天做了____个;20天做了____个;23天做了____个。