Natural resources a. are inputs provided by nature. b. include land, rivers, and mineral deposits. c. take two forms: renewable and nonrenewable. d. All of the above are correct.

d. All of the above are correct.

Explanation: Natural resources are resources provided by nature. They occur in nature without manmade interference. Natural resources include mineral deposits, land water bodies and the atmosphere. These resources are utilized by man for economic, social and educational purposes. Natural resources can be renewable or nonrenewable resources such as water are renewed by rainfall. Heavy manmade activities such as industrialization, war or natural disasters can deplete these resources.

cells use diffusion to get substances in and out of themselves. that diffusion will occur across the cell membrane or the outer covering of the cell. because we are talking about the surface of the cell, surface area and volume are  important factors here. as a cell increases in size, its surface area and volume increase as well.  we call that the surface area to volume ratio (sa: vol).  but the catch is that  volume increases at a greater rate than surface  area. in other words, as a cell gets bigger, the sa: vol gets smaller. so a really small cell like bacteria is mostly cell membrane (surface) with very little contents (volume). a really big cell like an egg, is mostly insides with a super thin membrane. so what ends up happening is that the cell cannot efficiently diffuse all of the stuff it needs in/out to survive. therefore cell size is limited to about 100mm. so how do we make organisms bigger than 100mm? cells divide! by dividing and becoming multicellular, organisms are able to grow!   check out the diagrams i attached to see the effect of sa: vol. i hope this ! good luck!