Name two safety measures to follow when attaching the side-arm of the round bottom flask to the condenser, using a one-holed rubber stopper.

a) a. Secure the rubber stopper tightly; b. Use a non-conductive material for the side-arm.
b) a. Apply lubricant to the rubber stopper; b. Ensure the side-arm is made of metal.
c) a. Lubricate the rubber stopper; b. Tighten the side-arm securely.
d) a. Use a two-holed rubber stopper; b. Attach the side-arm with a metal clamp.