根据短文内容，选择最佳答案。 Emilyand Alex were happy when their family moved to a house with a very big garden. Theycould climb up trees, grow flowers and even play badminton. They liked to watchthe birds flying among the trees in the garden. They even started to put food outto attract（吸引）more birds.
Everythingwas fine for a few days until one afternoon there was a strange bumping noise ona window. Emily went outside and found a small bird dead on the grass. Its neckseemed to be broken.
"Itmust have flown into the window," Alex said when his sister Emily called himto have a look. "Ah, yes, look here. You can see the mark where it hit thewindow. There are a couple of tiny feathers stuck(粘贴) on the window."
"Poorthing!" Emily said.
Duringthe next month, another five birds died in the same way. "Why would they flyto the windows?" they wondered. Finally they found out the truth. When thebirds were flying, they couldn't see into the rooms. All they saw was the reflection(反射) of the garden. They thought that they were flying into trees becausethey saw trees reflected by the window.
"Somethinghas to be done to save the birds." the parents decided.
At first,he family tried keeping curtains（窗帘）across the windows, but thismade the room dark. Then they bought some strong black paper and cut out the shapeof ahawk. They made six hawks—one for each window. They stuck the hawks to the windows. They lookedpretty and did not keep out much light. When the birds saw the hawks, they wouldfly away.
Afterthat, there were no more dead birds. The family were much happier.
