Accuracy of measurement of a physical quantity depends on which factors?

Choose the correct relation between $l_1$ and $l_2$ for the given allene molecule structure.

What is accuracy in measurement? Accuracy depends on which factors?

The nearest star to our solar system is $4.29$ light years away. How much is this distance in terms of parsecs? How much parallax would this star (named Alpha Centauri) show when viewed from two locations of the Earth six months apart in its orbit around the Sun?

If the angular diameter of the Sun is about $30'$ and its distance from the Earth is $1.5 \times 10^{11} \, m$,then the solar diameter is:

The angle subtended by a plate of diameter $2 \, cm$ at a distance of $1000 \, cm$ from the eye is ..... (in $^\circ$)