Chemistry · Some Basic Concepts of Chemistry

Consider a system of base units where the speed of light in vacuum \( c \) is fixed to \( 299792458 \text{ ms}^{-1} \). If a new unit system defines the time second in terms of the caesium hyper-fine transition frequency \( \Delta \nu_{cs} \), which of the following physical constants is explicitly used in the modern SI definition of the metre?

1. Planck's constant \( h \)
2. Boltzmann constant \( k \)
3. Avogadro constant \( N_A \)
4. Speed of light \( c \)