Hydrogen and carbon because they are the most common element of canyon
Explanation:
A change that does not cause any change in chemical composition of a substance is known as a physical change.
For example, mass, density, volume etc are all physical changes.
On the other hand, a change that brings change in chemical composition of a substance is known as chemical change.
For example, combustion, toxicity, reactivity etc are all chemical changes.
Hence, following statements are identified as chemical or physical changes as follows.
(a) Oxygen gas supports combustion : Chemical change
(b) Fertilizers help to increase agricultural production : Chemical change
(c) Water boils below 
on top of a mountain : Physical change
(d) Lead is denser than aluminum : Physical change
(e) Uranium is a radioactive element : Chemical change
Answer:
Forest Fire
Explanation:
Forest fire is an ecological factor over which biological processes like seed dispersal and their germination is dependent upon. Some plants germinate under high temperature underground regions of the soil which is covered by the hot soil affected by the burning by the forest fire. Some of the coniferous trees like longpole pines have hard cone which exhibit the seeds. These cones exhibit the serotonin resins which are melted by the forests fire hence fire helps in dispersal of the seeds. Other plants like Eucalyptus and Banksia are also dependent upon fire for seed dispersal.
Answer:
White phosphorusRed PhosphorusIt is insoluble in water but soluble in carbon disulphide.It is insoluble in both water and carbon disulphide.It undergoes spontaneous combustion in air.It is relatively
Explanation:
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