那栋旧楼的供暖系统效率低下。

The heating system in the old building was ___inefficient.

低效的客房服务导致了许多客人的投诉。

The ___inefficient room service led to many guest complaints.

他低效的学习习惯意味着他必须比同学学习更长时间。

His ___inefficient study habits meant he had to work much longer than his classmates.