Answer the following question: Read the article and select the best answer. Article: Entire populations of American toads breed within the same few days at the same time each year, usually late April or early May. The toads hop to their breeding ponds after the ground has warmed and the first hard spring rain falls. To get there, many of the toads will cross roads that cut through their habitat. It will be a grand view of hopping toads as well as a disastrous killing by cars! The toads are "slow in moving at that time of year--it's still cool, they've been inactive--and they get killed" by cars when crossing roads, said Serrao, a naturalist. An April night five years ago, when Serrao went out to a country road to watch the moving of the toads, he counted 100 toads; 95 were hit by cars. A similar story can be told for several other species of toads, frogs, crocodiles and turtles around the world. The world's amphibians are reducing, and road-killing is just one factor behind it. Other better-known causes of the decline include global warming, insecticides , and the loss of wetlands. Serrao says unless these animals get help crossing the road, their local populations will disappear. Jackson, a biologist, said one way to help amphibians survive road crossings is to construct "amphibian tunnels" beneath the road. Jackson says tunnels should be a 0.6-meter-by-0.6-meter box, open at the top, and fitted with an iron grate to allow enough air and light into the tunnel. In addition, fences or walls should extend out from either side of a tunnel for about 30 meters, which guide amphibians toward the tunnels. European countries have built amphibian tunnels for decades. Jackson led a team that installed the first such tunnel in prefix = st1 /Americain 1987, which helped over 3/4 of the local amphibian population safely cross the road. Jackson says that there are about a hundred amphibian tunnels in the UStoday, but many of them were not carefully designed and probably not working well because land developers wanted to save money. Question: When do American toads hop to breeding ponds? Options: A: Before the ground is warm. B: When the first heavy rain comes in spring. C: After it is cool in sunny summer time. D: When it is early April.
Answer:
B