Explanation
Dimension of work and torque = [ML2T–2]
Light year and wavelength both represent the distance, so both have dimensions of length not of time.
Addition and subtraction can be done between quantities having same dimensions.
Avogodro number (N) represents the number of atoms in 1 gram mole of an element ,i.e, it has the dimensions of mole–1.
As the distance of star increases, the parallax angle decreases, and great degree of accuracy is required for its measurement. Keeping in view the practical limitation in measuring the parallax angle, the maximum distance of a star we can measure is limited to loo light years.
The last number is most accurate because it has greatest significant figure 3.
As length, mass and time represent our basic scientific notations, therefore they are called fundamental quantities and they cannot be obtained from each other.
Because representation of standard metre in terms of wavelength of light is most accurate.
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