简述烧结原料的种类。
要想将不同图层中的对象对齐（背景层除外），首先应该（）。 ["将这些图层都合并","将这些图层都放到一个Layer Set（图层文件夹）中","将这些图层都链接起来","将这些图层都锁定"]
Gas turbines differ from steam turbines in that （）. ["steam rather than gas is used to turn a shaft","vapor rather than gas is used to turn a shaft","the former uses gas to turn a shaft","the latter uses gas to turn a shaft"]
如何用感官来评价淡水鱼的新鲜度？
实用化验收，对输电电缆试验记录无录入要求。
LED灯具产品研发需解决的问题是什么？
