Which of the following biomolecules is common to respiration-mediated breakdown of fats,carbohydrates and proteins?

If the vectors $a \hat{i}+\hat{j}+\hat{k}$,$\hat{i}+b \hat{j}+\hat{k}$,and $\hat{i}+\hat{j}+c \hat{k}$ $(a \neq 1, b \neq 1, c \neq 1, a \neq b \neq c)$ are coplanar,then the value of $\frac{1}{1-a}+\frac{1}{1-b}+\frac{1}{1-c}$ is:

Which of the following is responsible for the production of biogas?

$\int_0^3 \frac{3x+1}{x^2+9} dx$ is equal to :

If $b+c=3a$,then $\cot \frac{B}{2} \cot \frac{C}{2}$ is equal to :

Which one of the following is the most widely accepted method of contraception in India,at present?