Which of the following ions can cause coagulation of proteins?

$A$ body executes simple harmonic motion under the action of a force $F_1$ with a time period $T_1 = \frac{4}{5} \ s$. If the force is changed to $F_2$,it executes $SHM$ with a time period $T_2 = \frac{3}{5} \ s$. If both the forces $F_1$ and $F_2$ act simultaneously in the same direction on the body,what is its new time period in seconds?

Identify the correct decreasing order of the following with respect to altitude from the atmosphere:
$I$. Troposphere
$II$. Mesosphere
$III$. Thermosphere

Identify the organism shown in the given figure.

$A$ plank with a small block on top of it is undergoing vertical $SHM$. Its period is $2 \, s$. The minimum amplitude at which the block will separate from the plank is:

$A$ small quantity of solution containing $Na^{24}$ radio nuclide of activity $1 \, \mu Ci$ is injected into the blood of a person. $A$ sample of the blood of volume $1 \, cm^3$ taken after $5 \, hours$ shows an activity of $296$ disintegrations per minute. What will be the total volume of the blood in the body of the person? Assume that the radioactive solution mixes uniformly in the blood of the person. (Take $1 \, Ci = 3.7 \times 10^{10} \, dps$ and $e^{-\lambda t} = 0.7927$; where $\lambda$ = disintegration constant)