The synonym of the word "ambivalent" is

Here are the solutions to the questions:

19. The synonym of the word "ambivalent" is
The word "ambivalent" means having mixed feelings or contradictory ideas about something or someone. Therefore, the closest synonym is "undecided".
The correct option is B.
$\boxed{\text{B. Undecided}}$

20. The sum of all natural numbers from 1 to 100 is
To find the sum of the first $n$ natural numbers, we use the formula $S_n = \frac{n(n+1)}{2}$.
Here, $n = 100$.

$$S_{100} = \frac{100(100+1)}{2}$$ $$S_{100} = \frac{100 \times 101}{2}$$ $$S_{100} = 50 \times 101$$ $$S_{100} = 5050$$

The correct option is A.
$\boxed{\text{A. 5050}}$

21. PMJAY stands for
PMJAY stands for Pradhan Mantri Jan Arogya Yojana.
The correct option is B.
$\boxed{\text{B. Pradhan Mantri Jan Arogya Yojana}}$

22. The sum of a number and its square is equal to 72. The number is
Let the number be $x$.
According to the problem, the sum of the number and its square is 72:

$$x + x^2 = 72$$

Rearrange the equation into a standard quadratic form:

$$x^2 + x - 72 = 0$$

Factor the quadratic equation:

$$(x+9)(x-8) = 0$$

This gives two possible solutions for $x$:

$$x+9=0 \implies x = -9$$ $$x-8=0 \implies x = 8$$

Since the options provided are positive integers, the number is 8.
Check the answer: $8 + 8^2 = 8 + 64 = 72$.
The correct option is A.
$\boxed{\text{A. 8}}$

23. The phrase "wild goose chase" means
The idiom "wild goose chase" refers to a foolish, hopeless, or futile pursuit of something unattainable.
The correct option is A.
$\boxed{\text{A. Unproductive or useless work}}$

24. Which Article of the Constitution of India gives a citizen the right to vote in State Assembly/Parliamentary election?
Article 326 of the Constitution of India provides for elections to the House of the People and to the Legislative Assemblies of States to be on the basis of adult suffrage, granting every citizen who is not less than eighteen years of age the right to vote.
The correct option is C.
$\boxed{\text{C. Article 326}}$