Marie and Pierre Curie invented

Answer: Option B

Explanation:

Marie and Pierre Curie of France invented Radium in 1898,

Radio was invented by G. Marconi of England in 1901,

Radar was invented by Dr. A.H. Taylor and L.C. Young of USA in 1922,

Refrigerator was invented by J. Harrison and A. Catlin of Britain in 1834.

Answer: Option A

Explanation:

Machmeter - is used to determine the speed of an aircraft in terms of speed of sound,

Magnetometer - is used to compare magnetic movements and fields,

Micrometer - is used to convert sound waves into electrical vibrations.

Answer: Option D

Answer: Option A

Answer: Option A