Final answer:
In North America, plants are most likely to become dormant during winter due to low temperatures and the unavailability of water for growth.
Step-by-step explanation:
During periods that are unfavorable for growth, such as when temperatures are low and water is frozen and thus unavailable for plant growth, many plants in North American regions become dormant. The season in which these plants most likely lie dormant is winter. The arrival of cold weather and shorter days during winter serves as environmental signals for many plants to enter a state of dormancy. This physiological adaptation helps plants to conserve energy and survive through harsh conditions until favorable growing conditions return in spring.