8. Why is nitrogen used in fertilizer when there's so much N, in the air? O A. There's relatively little air underground.
O B. Ny is toxic to plants.
O C. It's a macronutrient, while gaseous N is a micronutrient.
O D. Plants can't use N2 from the air.

Agroup of students is studying convection currents. they fill two identical balloons with the same amount of helium. one balloon is placed in a freezer and the other in an area with warm air. after 10 minutes, the balloons are released from a height of 1 meter. which of the following do the students most likely observe? question 8 options: the cold balloon expands and rises. the warm balloon shrinks and sinks. the balloons rise at the same rate. both balloons are the same size. the ballons both rise. the cold ballon is larger than the warm balloon. the warm balloon expands and rises. the cold balloon shrinks and sinks.