On a backpacking trip, kenny hikes all day at a steady pace, covering 30 kilometers and burning 4000
calories. at the school track, janelle runs the 100-meter sprint in 13.5 seconds, burning 10 calories.
afterward, janelle's leg muscles are aching and she is breathing hard, while kenny maintains normal
breathing all day, even though he burns 400 times more calories than janelle. which two statements offer the
best explanation for this phenomenon?
a. if the aerobic pathway-cellular respiration cannot meet the energy demand, then the anaerobic
pathway-lactic acid fermentation-starts up, resulting in lactic acid buildup and oxygen debt.
b. aerobic cellular respiration produces more energy, but its use is limited because of lactic acid
buildup in the muscles and the resulting "oxygen debt."
c. after about 90 seconds of intense exercise, the muscles become depleted of oxygen, and
anaerobic respiration can no longer function to produce atp, resulting in "oxygen debt."
d. the rate of energy demand determines how the muscles will obtain energy, either from cellular
respiration or from lactic acid fermentation if not enough oxygen is present.

Mantle convection  is the slow  creepingmotion of earth's solid silicate  mantle  caused by  convection  currents carrying  heat from the interior  to the planet's surface.[1][2]  the earth's surface  lithosphere, which rides atop the  asthenosphere  (the two components of the  upper mantle), is divided into a number of  plates  that are continuously being created and consumed at their opposite  plate boundaries. accretion occurs as mantle is added to the growing edges of a plate, associated with  seafloor spreading. this hot added material cools down by  conduction  and  convection  of heat. at the consumption edges of the plate, the material has thermally contracted to become dense, and it sinks under its own weight in the process of  subduction  usually at an  ocean trench.[3]this subducted material sinks through the earth's interior. some subducted material appears to reach the lower mantle,[4]  while in other regions, this material is impeded from sinking further, possibly due to a phase transition from  spinel  to  silicate perovskiteand  magnesiowustite, an  endothermic reaction.[5]the subducted oceanic crust triggers  volcanism, although the basic mechanisms are varied. volcanism may occur due to processes that add buoyancy to partially melted mantle causing an upward flow due to a decrease in density of the partial melt.secondary forms of convection that may result in surface volcanism are postulated to occur as a consequence of intraplate extension[6]  and  mantle plumes.[7]it is because the mantle can convect that the  tectonic plates  are able to move around the earth's surface.[8]mantle convection seems to have been much more active during the  hadean  period, resulting in gravitational sorting of heavier molten  iron, and  nickel  elements and  sulphides  in the core, and lighter  silicate minerals  in the  mantle.

Volcanoes make new rocks so not ahotspots are the the stuff that makes volcanoes mid atlantic ridge(mar cause i’m lazy) is a constructive plate boundary so it makes sense that new rocks would be found near it, also the mar is in the middle of the ocean so it fits the description deep ocean trench, umm, there’s no ocean trenches to where you’re goingso the mar is most likely the answeri wouldn’t trust me but hey why not