Perfect information implies that all buyers and all sellers are completely informed about the price, quality and other relevant details about the product, as well as the market. These features result in the single most distinguishing characteristic of perfect competition, that is ......

Price taking behaviour.

The correct answer is Option (3) → Price taking behaviour.

Perfect information ensures that all buyers and sellers know the prevailing market price and product characteristics. Because of this, no individual buyer or seller can influence the price, which leads to price taking behaviour — the defining feature of perfect competition.