Because we hear so many sounds simultaneously, the first stage of listening is to:

receive the sound and then filtration of the messages to avoid confusion.

Explanation:

Active listening process is into five stages: 1) receiving the message, 2)understanding, 3)remembering 4) evaluating the selected message, and 5) response to the message.

Receiving is the first stage of the listening skill which involves the hearing of the message and then filtration of the message. The hearing of the message involves the focused attention while filtration of the message involves the isolation of the message from a mixture of messages. The filtration is performed to avoid the mixing of the stimuli.

Thus, receive the sound and then filtration of the messages to avoid confusion is the correct answer.

answer: substrate concentration. enzymes work best when there is a high enough substrate concentration for the reaction they catalyse.