Answer: 2. cannot be an element.
Explanation:
Element is a pure substance which is composed of atoms of similar elements.It can not be decomposed into simpler constituents using chemical reactions.Example: Copper 
Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass.It can be decomposed into simpler constituents using chemical reactions. Example: methane 

Thus as it can be decomposed into its constituent elements, it is a compound.
Mixture is a substance which has two or more components which do not combine chemically and do not have any fixed ratio in which they are present.
Thus methane cannot be an element.
Answer:
the stem, but if its more specific xylem cells
Short answer: nitrogen, oxygen, Argon, and
inert gas
The atmosphere contains many gases, most in small amounts, including some pollutants and greenhouse gases.
These contribute to climate change.
Landslides and slumps are forms of mass movements. Types of erosion both move, in different ways. In slumps, land breaks off in one piece, or chunk. Landslides are when rocks and dirt rapidly move down a slide.
Extreme weather e.g. snow and cold weather. Another main contributing factor is that many places have a long dry season.