Answer:
1) Methyl orange
Explanation:
Acid base indicators are solutions of certain dyes that bring about a color change at a certain pH i.e. the at a particular H+ ion concentration.
The color change and the pH range for the four indicators mentioned in the question are as follows:
indicator pH range color change
1. Methyl orange 3.2-4.4 red-yellow
2. Bromothymol blue 6.0-7.6 yellow-blue
3. Bromocresol green 3.8-5.4 yellow-green
4. Thymol blue 8.0-9.6 yellow-blue
Based on the above data, only methyl orange is yellow at pH above 4.4. Hence, indicator is yellow in a solution with a pH of 9.8 is methyl orange