Did you know the roller skate has been around since early 1700s? people who loved winter ice-skating wanted to go "dry land skating" in the summer, and so they attached wheels to their boots. the early models were hards to roll, though. in the late 1800s, roller-skate design improved. once the skaters were easier to handle, he sport became more popular.

which of these best states the main idea of the passage?

a) people liked ice-skating in the winter
b) many people wanted to skate in the summer.
c) roller-skating has become a popular sport over time
d) early roller skates were difficult to use

Ameadow ecosystem includes many species of grasses and small shrubs, several herbivores, and a few carnivores. a fungus colonizes the meadow and kills most of its vegetation. what is most likely to happen to the populations of herbivores and carnivores in the ecosystem? a. the populations of herbivores and carnivores will increase because there will be less competition for chemical energy. b. the populations of herbivores and carnivores will remain stable because the fungus cannot infect these organisms. c. the populations of herbivores will decrease because of vegetation loss, but the population of carnivores will remain stable. d. the populations of herbivores and carnivores will decline because less chemical energy will be stored in the ecosystem.

Ascientist discovers a new body between the orbit of neptune and the kuiper belt. the object is round and travels in an orbit around neptune with other space objects. the scientist claims that she has found a new dwarf planet. where is the scientist’s error?

How can antibodies "remember" a particular bacterial invader or "antigen" on that invader?