Can aniline be nitrated directly?

Yes.

Explanation:

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In this according to the attached file, we infer that the aniline can be nitrated by the addition of nitric acid and in presence of sulfuric acid that provides an acidic media. It leads to the formation of o-nitroaniline, m-nitroaniline and p-nitroaniline whereas the major products are the last two due to the steric hindrance.

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the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.

its first and third is your answer i did the qustion the fourth isnt right