Please help I cant get it

An ambulance emits a frequency of 450 hz from its siren. what frequency is heard by a man as the ambulance moves toward him? less than 450 hz more than 450 hz 450 hz 0 hz

Carbon-14 is a radioactive element that undergoes beta decay. which force is responsible for allowing carbon-14 to become stable? electromagnetic gravitational weak nuclear strong nuclear

If a simple machine reduces the strength of a force, what must be increased?