People diamonds with crystal. (imitation)

What's right about the general properties of crystal? A: If there are anions in a crystal, there must be cations B: If there are anions in a crystal, there must be cations C: There are not necessarily chemical bonds in molecular crystals D: There must be no covalent bond in the ionic crystal

​An ionic crystal consists of cations and anions, therefore, the ionic crystal can conduct electricity.‍

在Scopus数据库的高级检索中，检索期刊名称中包含"polymer",同时论文题目中含有"crystal"的文献，正确的检索式为： A: SRCTITLE(polymer) and TITLE(crystal) B: SRCTITLE=polymer and TITLE=crystal C: polymer wn journal and crystal wn ti D: polymer/st and crystal/ti

The sequence of reagents used in Gram staining is () A: Safranin solution → iodine solution → alcohol →<br/>crystal violet B: crystal violet → alcohol → iodine solution → Safranin<br/>solution C: Crystal violet → iodine solution → alcohol → Safranin<br/>solution D: Safranin solution → alcohol → crystal violet → iodine<br/>solution E: Safranin solution → crystal violet → iodine solution →<br/>alcohol

Solid<br/>materials can be classified into the following types ( ) A: Amorphous B: Polycrystalline C: Single<br/>crystal D: Mixed<br/>crystal

中国大学MOOC:"公司在第1年的第2季度开始研发Crystal产品，公司用全自动线生产Crystal，原材料准备充足，则最早可以在 生产出1个Crystal。";

Snowflakes have six angles and crystal clear.

某公司第3年在区域市场投放了Beryl和Crystal的广告费，均为1M，在国内市场投放了Crystal的广告费，为1M。该公司在国内市场可以拿到的订单是（ ）。 A: Beryl B: Crystal C: Ruby D: Saphire

中国大学MOOC:"Crystal的研发投入为（ ）。";