Question

21 multiple choice 1 point
how have humans altered the carbon cycle and affected aquatic ecosystems?
all of the choices are caused by human activity.
burning fossil fuels increases co₂ which affects ocean ph and aquatic life
the ocean has absorbed more than 90% of the extra heat trapped by greenhouse gases and atmospheric co₂ causing bleaching of the coral reefs.
none of the choices are caused by human activity.
runoff from agriculture and urban areas can fuel algal blooms. their decomposition releases excess co₂ back into the atmosphere.

Explanation:

Burning fossil fuels (human activity) increases CO₂ (ocean acidification affects pH/aquatic life). Ocean absorbs heat (human - caused GHG) causing coral bleaching. Agricultural/urban runoff (human) causes algal blooms (decomposition releases CO₂).

Answer:

All of the choices are caused by human activity.