3. using upper and lowercase letters (Sentence case)
4. using a serif font
Explanation:
Readability on a website is very important for a website designer and also for the user. If a user wants content on his/her website to be read, he/she needs to do some research on what works and what doesn't. For each of the option in the question, there are guidelines to using them. for example, font size sometimes depend on the font style used: as some font style are more bigger than orders. Therefore, to get good readability on a website,font face, font size, color, sentence structure, all need to be considered before designing the website.
