Choose the correct answers below: Of at Out on

Read the passage and choose the correct word or phrase that best fits each of the numbered blanks. 

Many tall office buildings leave their lights (31) ________ at night, a wasteful practice that has lethal consequences for migrating birds. Confused by the lit windows, millions of birds slam into tall buildings and die every year, says a conservation ecologist at the Chicago Field Museum. He and his colleagues quantified the losses by counting the number of birds (32) ________ hit McCormick Place, a 90-foot-tall glass convention centre in Chicago. Over the last two years, 1,297 birds - mostly sparrow, warblers, and thrushes - perished after flying into (33) ______ windows. During the same period, only 192 died after hitting dark windows, (34) __________ the windows were unlit nearly half of the time during the study. The deaths place an additional strain on declining species such as wood brushes. " This is just another pressure that birds don't need," says the ecologist. Since most window collisions occur during the peak migratory times after midnight, he (35) _________ that skyscrapers turn out their lights from 11 p.m. until dawn during the two migration seasons, from late March through May and from mid-August to Thanksgiving. A seasonal light-out campaign would also reduce the buildings' electricity bills. 

Choose the correct answers below: Of at Out on

• A. of 
• B.  at 
• C. out 
• D. on