Which argument(s) for the increasing use of solar energy is/are valid?
i. solar cells are becoming cheaper and increasingly more efficient.
ii. the cost of generating electricity from fossil fuels is increasing.
iii. limited and uncertain supply and the increasing requirements for pollution control are raising the cost of fossil fuels.
a. i only
b. ii only
c. i and iii only
d. i, ii, and iii

Option D is correct.

Explanation:

Option D is correct.

Solar cells are replacing the conventional ways of making electricity. They are getting cheaper with each coming day. Secondly they use the renewable energy which causes no pollution and is available in large amount as our sun is a continuous source of energy. Another reason fossil fuels are getting out of fashion because they require huge setups and initial cost. Their burning emit green house and other toxic gases which cause rise in temperature and pollution. Also their amount is decreasing which make it expensive to use.

explanation:

let the different atoms be x and y. each with four protons and same mass will be represented as follows.

mass number is number of protons + number of neutrons.

            and  

since, it is given that one has a negative charge while the other is neutral. therefore, there will be increase in number of protons and the atom will be represented as follows.

according to periodic table, mass number of beryllium is 9 and it has atomic number 4 so, the atoms will be and .  

the protons and neutrons will be located inside the nucleus whereas the electrons will be revolving around the nucleus.  

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