Which of the following pairs of organs consists only of endocrine glands?

In a reaction,$A + B \rightleftharpoons C + D$,$40 \%$ of $B$ has reacted at equilibrium,when $1 \ mole$ of $A$ was heated with $1 \ mole$ of $B$ in a $10 \ L$ closed vessel. The value of $K_C$ is

Which one of the following elements is not an essential micronutrient for plant growth?

An image formed by a concave mirror of focal length $6 \ cm$ is $3$ times the size of the object. What is the distance of the object from the mirror in $cm$?

The condition that $f(x)=a x^3+b x^2+c x+d$ has no extreme value, is

Identify the product $(A)$ of the following reaction: $C_2H_5-O-C_2H_5 + CO \xrightarrow[500 \ atm]{BF_3 / 150^{\circ}C} A$