Need help kinda confused

Which of the following is a limitation of a clinical trial? a.)amount of random assignments b.)hospital cost c.)number of test tubes d.)amount of peer review

Need with these questions . need the answers in a rush for these questions are the answers i put down are correct or not? ?

Match the correct terms to their descriptions a system in which only energy but not matter is exchanged frozen water in snow part of geosphere that includes only soil a thin layer between the troposphere and the stratosphere cryosphere tropopause closed system pedosphere