Answer:
correct option is C) 2.8
Step-by-step explanation:
given data
string vibrates form = 8 loops
in water loop formed = 10 loops
solution
we consider mass of stone = m
string length = l
frequency of tuning = f
volume = v
density of stone =
case (1)
when 8 loop form with 2 adjacent node is
so here
..............1

and we know velocity is express as
velocity = frequency × wavelength .....................2
= f ×
here tension = mg
so
= f ×
..........................3
and
case (2)
when 8 loop form with 2 adjacent node is
..............4

when block is immersed
equilibrium eq will be
Tenion + force of buoyancy = mg
T + v ×
× g = mg
and
T = v ×
- v ×
× g
from equation 2
f ×
= f ×
.......................5
now we divide eq 5 by the eq 3

solve irt we get

so
relative density 
relative density = 2.78 ≈ 2.8
so correct option is C) 2.8
$1.14 1.40 x 0.8=1.12 1.4+ 1.12=1.52 * 0.25 = 1.14
V=s³
SA=6s²
sub 2 for s
V=2³=8 cubic inches
SA=6(2²)=6(4)=24 square inches
E: 36 because the total degrees of a parallelogram is 360 and opposite angles of parallelogram’s are equal so the angles diagonal from the given ones are the same. So the corners are 3x, 2x, 3x, 2x. In total that is 10x. 360/10 = 36