The primary problem is the greenhouse effect. Greenhouse effect is when some gases (including CO2) absorbs some portion of sun's heat to make the atmosphere warm to support life. But when the amount of CO2 etc. increases in the atmosphere, it heats up more than it is required. So, by limiting CO2 emission, we can solve this problem.
The answer is number two I think
Answer:
Phrase, Idiom or Sentence
Explanation:
A sequence of words that form a meaning can be a phrase, idiom or a sentence.
A phrase is a group of words that form a meaning. It can be a combination of a preposition and a noun, or an adjective and a noun. <em>Prepositional phrase</em> is for example "in the air", and an <em>adjectival phrase</em> is "a beautiful girl".
An idiom is a phrase that when formed, changes the meaning of the words in a phrase. For example,<em> "It's raining cats and dogs".</em> This sentence doesn't mean that literally cats and dogs fall from the sky, but it has a different meaning, which is <em>"It is heavily raining." </em>
A sentence is a group of words that must consist of at least subject and a verb, which can be followed by other words or phrases. For example, a phrase is <em>"a beautiful girl"</em> - it cannot be a sentence because it doesn't have a verb. If we say <em>"A beautiful girl is here."</em> - we make a sentence, because now it has a <em>subject (A beautiful girl), a verb (is) and a preposition of place (here). </em>
