What is meant by the angular diameter of the moon?

What is called a basis? What is parallax? Define angular diameter.

The angle of $1^{\prime}$ (minute of arc) in radian is nearly equal to

The mean distance of the sun from the earth is $1.5 \times 10^8 \text{ km}$ (nearly). The time taken by the light to reach the earth from the sun is.....$\text{min}$

$A$ celestial object is observed from two points $A$ and $B$ on the Earth,which are diametrically opposite. The angle between the two observation directions is $2.9 \times 10^{-4} \text{ rad}$. Taking the diameter of the Earth to be $1.28 \times 10^4 \text{ km}$,find the distance between the Earth and the object.

The true length of a wire is $3.678 \,cm$. When the length of this wire is measured using instrument $A$,the length is $3.5 \,cm$. When the length of the wire is measured using instrument $B$,it is found to be $3.38 \,cm$. Then,the: