Which of the following is a non-metal?

Ca
AS
Ро
Ca
O

Hydrogen and helium are both members of?

Two forces produce equal torques on a door about the door hinge. the first force is applied at the midpoint of the door; the second force is applied at the doorknob. both forces are applied perpendicular to the door. which force has a greater magnitude?

What is a subatomic particle with a negative charge and very little mass?