A barometer kept in an elevator reads 76 cm when the elevator is accelerating upwards. The most likely pressure inside the elevator (in cm of Hg) is

The total of a and g will be the net acceleration while the elevator is moving upward at acceleration. A device known as a barometer is used to measure atmospheric pressure, also known as barometric pressure.
i.e.$a+g$

Let this mercury column's height be $h=76 \mathrm{cm}$.
Allow mercury's density to be $\rho$.
Let the gravitational acceleration be g.
Let a be the lift's acceleration.

A mercury-dipped tube serves as a barometer.
The mercury column inside the tube rises to a certain height as a result of the external air pressure.
You may provide the ambient pressure as
$p_A=h\rho g$
The effective value of g may be calculated using the following formula if the lift uniformly accelerates upward:
$g_{eff}=g+a$
Consequently, the lift's effective pressure may be expressed as
$p_{eff}=h\rho (g+a)$
Since the $g_{eff}>g$, The value of h must drop in order to maintain the constant effective pressure.
However, it is assumed that h will always have the same value.
As a result, effective pressure must be worth more.
$\therefore p_{eff}>p_A$
$\Rightarrow p_{eff}>76 \mathrm{cm}\text{ of }\mathrm{Hg}$
Consequently, the elevator's internal pressure has to be higher than$76 \mathrm{cmofHg}$.

Hence, the correct answer is option C.