In the given question, a part of the sentence is bold. Four alternatives for the bold parts that may improve the sentence are given below. Choose the correct alternative. In case no improvement is needed, then choose 'no improvement'.

Hitler was an absolute potentate.

Out of the four alternatives, choose the one which can be substituted for the given word or sentence.

A drug or other substance that induces sleep.

Out of the given four alternatives, choose the one which can be substituted for the given word/sentence.

A speech delivered without any preparation.

Out of the given four alternatives, choose the one which can be substituted for the given word/sentence.

Animal that eat flesh.

Out of the four alternatives, choose the one which can be substituted for the given words/sentences.

A fictious name especially one assumed by an author.

Out of the given four alternatives, choose the one which can be substituted for the given words/sentences.

Animals which suckle their young ones.

Find the sum of first five terms of the following series:

$\frac{1}{1\times 4}+\frac{{\displaystyle 1}}{{\displaystyle 4\times 7}}+\frac{{\displaystyle 1}}{{\displaystyle 7\times 10}}+.......+......$