According to the chart given estimate the useful range for each indicator, from a minimum to maximum ph. the range usually spans 1.5 to 2 ph units. for example, bromphenol blue is considered to be useful in the range from 3.0 to 4.6.
what would be the best indicators used for ph= 2, ph= 4, and ph= 6?

Hello! So to answer your question all the answers can be found within the above chart provided. Simply compare and contrast the pH levels in which the indicators changed color.
So doing that we can conclude the followoing pertaining to our indicators. Bromothymol blue    5.3-7.3
Methyl yellow    2.4-4.3
Bromocresol green    3.3-5.3
Red cabbage extract    3.3-5.3

For your second question it is the exact same concept, but we can just look at our answer for the first question to conclude which indicator would be best used for those ph levels.
 Comparing and contrasting we can see that  the best indicator to use for observing PH changes around pH= 2 would be Methyl yellow,
 for around pH=4 would be Bromocrescol green,
 and for pH= 6 it would be Bromothymol blue.

If you have any other questions or would like further explanation just let me know! :)

Maybe you should get some from your teacher and learn more so you can get your grades up and maybe study a bit more