In the atomic model that includes a nucleus, the positive charge is OPTIONS:
- spread evenly throughout the model.
- located at multiple sites in the model.
- concentrated in the center of the model.
- positioned outside the center of the model.
A: concentrated in the center of the model.

Unequal distribution of the hormone auxin in plants helps to regulate the direction of plant growth. Which of the following is accomplished by plants in regulating the distribution of auxin? OPTIONS:
- pollination of flowers
- transportation of nutrients
- discouraging predation
- responding to the environment
A: responding to the environment

A student wants to find the most accurate account of a scientific discovery that took place within the past three months. In which of these sources should the student look? OPTIONS:
- newspapers
- magazines
- science textbooks
- science journals
A: science journals

Which distance is the smallest for which it is most practical to use the light-year as a unit of measurement? OPTIONS:
- the distance between Earth and its Moon
- the distance between Jupiter and the Sun
- the distance between the Milky Way and the nearest galaxy
- the distance between the Sun and the center of the Milky Way
A:
the distance between the Sun and the center of the Milky Way