What can commonly cause a drain to become clogged?

The correct answer highlights common causes of drain clogs, which include grease buildup, hair accumulation, foreign objects, and tree roots. Grease can accumulate in pipes over time, particularly in kitchens, where it may solidify and hinder water flow. Hair is notorious for getting caught in drains, especially in bathrooms, leading to blockages. Foreign objects such as paper products, toys, or any non-flushable items can inadvertently be flushed down the toilet or washed down sinks, contributing to clogs as well. Tree roots are another significant factor; as they seek water, they can penetrate underground plumbing systems, causing blockages and even damage to pipes.

The other options focus on situations that either do not lead to clogs or are not typical causes. Regular maintenance and cleaning actually help prevent clogs, while excessive cold weather can cause pipes to freeze, not necessarily clog them in the traditional sense. Heavy rainfall can lead to flooding but is not a primary cause of drain blockages in the context of everyday plumbing issues.