警察在黑暗的巷子里巡逻。

The police officer is ___patrolling a dark alley.

警察正在街上巡逻以确保安全。

The police officers are ___patrolling the streets to ensure safety.

警察每晚都会在公园巡逻以确保安全。

The police officers are ___patrolling the park every night to ensure safety.