In a series of chemical reactions, X→Y→Z→A, X converts to Y, Y converts to Z, and Z converts to A. Which term describes the process if the production of A interferes with the conversion of X to Y? OPTIONS:
- a complimentary response
- a control system
- negative feedback
- positive feedback
A: negative feedback

A pharmaceutical company has published the results of a limited experiment investigating the protective value of a chemical compound against high doses of UV rays on skin cells. It was later discovered that the results were not reproducible. What action could the company researchers have taken to avoid publishing erroneous results? OPTIONS:
- Perform multiple trials.
- Use only low levels of radiation.
- Use different wavelengths of radiation.
- Look into results of similar experiments before forming a hypothesis.
A: Perform multiple trials.

Which event most changes an ecosystem in a single day? OPTIONS:
- drought
- succession
- decomposition
- wildfire
A: wildfire

The concept of continental drift, continents drifting over the ocean floors, was proposed by Alfred Wegner in 1915. This concept was replaced by the theory of plate tectonics in the 1960s. Changes from the continental drift concept to the plate tectonics theory required which of the following? OPTIONS:
- strong earthquakes occurring along fault zones
- data and ideas being shared among scientists
- a scientific law being passed by Congress
- teachers beginning to teach the newer theory
A:
data and ideas being shared among scientists