Match the items in group A with the items in group B:

Sl.No.	Group – A	Group – B
1.	Small dimensions	Kilometre
2.	Large dimensions	Screw gauge
3.	Long distance	Scale
4.	Small distance	Light year
		Altimeter

One astronomical unit is the mean distance between the centre of the Earth and centre of the _________ i) Moon ii) Sun iii) Mars

Correct the mistakes if any, in the following statements:

i) Astronomical unit is the mean distance of the surface of the sun from the surface of the earth.

ii) Light year is the distance travelled by light in one year in vacuum at a speed of 3x10⁸m per minute.

Fill in the blanks:

The special methods adopted to determine very large distances are _________and (Laser pulse method, Light year method, Radio echo method, Astronomical method)

Least count of a screw gauge is an important concept related to screw gauge. What do you mean by the term least count of a screw gauge?