Which do you think is more likely: humans visiting an alien planet or aliens from another planet visiting us?

Which of the following is an example of an environmental change the affected the evolution of life a. volcanic activity b. changes in climate c. mountain building d. all of the above

Enzyme speed up chemical reaction are which type of marcomolecule? a.carbohhydrates b.protiens c.lipids d.nucleic acids

Nasa scientists must work together to make sure that everything is correct and accounted for when launching a shuttle. besides a physicist, what other type of scientist would be in making sure that the shuttle has the appropriate type and amount of fuel to reach its destination?