#1 is too vague and casual. #2 uses slang that wouldn't be used in a college application. #3 uses dated wording.
This leaves us with #4, which offers a personal reason for volunteering ("my grandfather had a heart attack") and is overall written formally. Thus, this would be the most appropriate style and tone for such an essay.
The root word Chron means time
Answer:
d. each participant receives one level of the independent variable.
Explanation:
Between-subjects design: The between-subjects design is also referred to as between-groups design and is one of the types of experimental design. In a between-subjects design, a single participant is exposed to only one user interface because each participant is supposed to test a single condition. It means that a single participant will experience one experimental condition.
Example: A researcher has two different groups of participants, one group is being experimented in a warm condition and the other is in cold condition.