Correct Answer  Option 3 : Cavendish
The correct answer is option 3) i.e. Cavendish
CONCEPT:

Law of Universal Gravitation: It states that all objects attract each other with a force that is proportional to the masses of two objects and inversely proportional to the square of the distance that separates their centres.
It is given mathematically as follows:
\(F = \frac{Gm_1m_2}{R^2}\)
Where m1 and m2 are the mass of two objects, G is the gravitational constant and R is the distance between their centres.
 The gravitational constant G establishes a relationship between gravitational force, mass, and distance.
 The value of G is 6.67 × 1011 N kg2 m2.
EXPLANATION:
 The value of G is obtained from Cavendish's experiment.
 The Cavendish experiment is based on torsion balance to measure the weak gravitational force between lead balls.
 The torsion balance consists of a bar suspended at its middle by a thin wire.
 The twist of the wire is measured which is then incorporated in the forcetorsion equation of the system to find the value of G.
 So, the value of G was first established by Cavendish and it is universally accepted.