Question

缩写后面的句号"."是否可以省略？比如“... etc.."还是"... etc."

Answer 1

不可省略，这是一种形式

Answer 2

英专学生的困扰，今天终于看到权威的，希望大家根据权威来使用标点。
Use a period with abbreviations:
Dr. Espinoza arrived from Washington, D.C., at 6 p.m.
Notice that when the period ending the abbreviation comes at the end of a sentence, it will also suffice to end the sentence. On the other hand, when an abbreviation ends a question or exclamation, it is appropriate to add a question mark or exclamation mark after the abbreviation-ending period.
粗略的翻译：若以缩略词来结束一句话，一个点同时也足以表达句子结束。若缩略词后需要加感叹号或者问号，可以加上这些标点。
摘自:http://blog.sina.com.cn/s/blog_4ec4273e0100gsdc.html

Answer 3

...etc.