Final answer:
The primary advantage of a passive investment strategy is lower transaction costs due to less frequent trading when compared to an active strategy.
Step-by-step explanation:
The main advantage of a passive investment strategy is B) Lower transaction costs. A passive strategy generally involves mimicking a market index and making fewer trades, thus reducing the costs associated with buying and selling securities frequently. This approach contrasts with an active strategy where the goal is to outperform the market, which often involves higher transaction costs due to more frequent trading. Moreover, with fewer trades and a long-term market-matching strategy, passive investing might lead to more predictable outcomes, aligning with the market's general upward trend over time.