Answer:
a control variable is a variable or an element wich is held constant throughout an experiment o a research in order to assess the relationship between multiple variables.
Answer:
He was a policeman in New York City.
He was a police officer in New York City.
The chairlady was wearing a beautiful clip in her hair.
The chairperson was wearing a beautiful clip in her hair.
Explanation:
That would be an exclamation mark.
Interjections express emotion....eww ! , yuck !, wow !, good grief !
