A panic attack can occur at anytime even in the absence of a stimulus.

An equinox occurs when a. neither end of earth's axis is tilted toward or away from the sun. b. the north end of earth's axis is tilted away from the sun. c. the north end of earth's axis is tilted toward the sun. d. earth's axis is parallel to the sun's rays. select the best answer from the choices provided a b c d

How is sound energy produced a. vibrating objects b. objects being heated c. temperature differences d. stationary objects

If the chemical properties of a substance remain unchanged and appearance or shape of a substance changes it is called a ?