Final answer:
Guilds were controversial because they restricted economic competition by controlling trade and production, which created significant barriers to market entry for non-guild members.
Step-by-step explanation:
Guilds became controversial primarily because they restricted economic competition (c). This controversy stems from the guilds' tendency to control the trade and production in various crafts, which led to significant barriers for newcomers wanting to enter the market. To keep a tight grip on their crafts, guilds often changed their rules so that only relatives of current masters could progress to high-level positions. This exclusivity meant that even though some labor shortages led to a relaxation of rules regarding guild membership, the possibility of moving up within a trade remained significantly limited for those not already connected to established guild members. This ability to restrict competition and maintain control over trade ultimately became a significant point of contention in the broader economic and social landscape of the time.