1. Typeform.
Only has Jump logic, i.e., jump to another question based on the answer to the current question.
2. Google forms
Only has Jump logic, i.e., jump to another question/page based on the answer to the current question.
3. Client Heartbeat
This survey is used to estimate customer's satisfactions about business or work. It seems not applicable to our bug report management study.
4. Zoho Survey
This survey can help us automatically display some questions based on previous answers. One disadvantage is that we cannot randomly select two questions for participants to answer. Besides, we cannot format the text.
5. SurveyGizmo
Only 1000$/year version can meet our request of randomly selecting two questions to answer.
6. SurveyPlanet
This survey's pro version can format text. But only by bold and italic.
The pro version is 20$/month. And it can help us automatically display questions based on previous answers. Again, we cannot use it to help us randomly select two questions to answer.
7. questionPro
本来这个工具应该是可以random的，但不知道为啥设置block，random时总会出问题。且要99$/month..还没法系统随机2个选择
8.eSurvet.org
这个是完全免费的，但逻辑功能太简单，只有skip logic。
9.Survey Face
这个的逻辑功能也很简单。
10. Smart survey
这个可以搞定随机显示几个问题。但只有skip ligic，没有关联逻辑，无法让问题根据前面的回答设置是否显示。。
11. Jotform
这个太简单了。。不适合。。
12. SoGoSurvey
这个本来使用起来很容易，可无法对一页里的某些questions随机。
真的是蛋疼啊。。
