These do not support the main idea of a paragraph. they do not focus on the main idea and may mislead or confuse the reader. they are called

The correct answer is irrelevant sentences.

Irrelevant sentences are sentences that doesn't apply to the subject stated in an idea or paragraph, hence the word "irrelevant". Something irrelevant does not go with the subject or thought being talked about. Irrelevant Sentences may only confuse the readers, so it would be best to be careful in writing your sentences, to not misdirect the readers. 

The changes to agriculture in the united states since 1900 is that increased mechanization has increased food production, thereby increasing the need for labor. there has been an increased need for higher speeds of food production due the fact that the population in the united states continues to rise.