13. As the frequency goes higher than 6 KHz, what must happen in order for the person to hear the sounds? *
1 The person needs to focus more and pay better attention to the test.
O
There does not need to be any changes to the sound for the person to hear those
frequencies.
O The amplitude (or volume) must be increased.
O The amplitude (or volume) must be decreased.

How can fertilizer use be detrimental to the environment? a. it can enter waterways, causing them to accumulate an excess of nutrients. b. high levels of fertilizer in bodies of water can lead to excess algal growth. c. fertilizer can lead to oxygen depletion, and be harmful to organisms in waterways. d. all of the above select the best answer from the choices provided a b c d