Which sentence best describes the process of convection? a. a rock melts when magma touches it. b. sunlight travels through space. c. water vapor in the air forms liquid water. d. cool air sinks, which forces warm air to rise.

Ivan is looking at a cross section of a stem taken from a vascular plant. he sees two different types of vascular tissue: the xylem, which is closer to the center of the stem, and the phloem, located around the xylem, closer to the outside of the stem. how do these two structures work together in a living plant?