Underline a mistake in the sentence and correct it

Underline a mistake in the sentence and correct it.)
11. We will go to Gray Caves on our trip.
(Make a question for the underlined part)
12. We can go hiking and rafting there.
(Turn the sentence into negative form)
13. What can we do to save the environment?
(Write the answer to the question using your own ideas)
14.Let's bring a flashlight and bottled water.
Why don't we bring a flashlight and bottled water.
(Rewrite the sentence, beginning as shown, so that the meaning stays the s
15. Your friend throws away old clothes.
(Give advice to your friend, using "should" or "shouldn't")