Right answer:
a. esta
We use demonstrative adjectives, such as este, ese and aquel when demonstrating a quality about the noun they modify. Here that quality is the location in respect to the speaker or the listener. Since the noun of this sentence is camisa (shirt), which is feminine and singular, then the only demonstrative adjectives, from the options, that meets this requirement is esta. So esta (that comes from este) is used to point out something (a feminine singular noun) near to the speaker in space or time. On the other hand, aquella (that comes from aquel) indicates something that is far away from both the speaker and the listener. Finally:
No me gusta esta camisa. Me gusta aquella amarilla.
