If my problem statement is: Which mask filters air more effectively?

And my independent variable is: Type of mask

What's my dependent variable?

Agas in a balloon at constant pressure has a volume of 160 ml at -125*c. what is its volume at 29.0*c?

What type of electromagnetic radiation has a shorter wavelength than blue light

Ageochemist examines a piece of metal that he found in the soil. he performs tests to identify the metal from its density, electrical conductivity, and melting point. which statement best describes his investigation? a. he is determining physical properties that are sufficient to identify the metal.b. he is determining chemical properties that are sufficient to identify the metal.c. he is determining physical properties that are insufficient to identify the metal.d. he is determining chemical properties that are insufficient to identify the metal.