The surface of the lake is at $2^{\circ}C$. Find the temperature of the bottom of the lake in $^{\circ}C$.

The characteristics of a molecular probe are:
$I$. Very long molecule
$II$. Double-stranded
$III$. $DNA$ or $RNA$
$IV$. Complementary to a part of desired gene
The correct pair is:

From which of the following do epithelial tissues originate?

The coordinate axes are rotated through an angle $135^{\circ}$. If the coordinates of a point $P$ in the new system are known to be $(4, -3)$,then the coordinates of $P$ in the original system are

The $pK_a$ values of four carboxylic acids are $4.76, 4.19, 0.23$,and $3.41$ respectively. The $pK_a$ value of the strongest carboxylic acid among them is

Consider the depicted hydrogen $( H )$ in the hydrocarbons given below. The most acidic hydrogen $( H )$ is