They are substitution reactions
hope that helps
Answer:
The correct option is the option;

Explanation:
The wavelength of a wave is the distance between two successive crests of the wave
Therefore, the wavelength, λ, is given by the fraction of the velocity, <em>v</em>, of the wave divided by the frequency, <em>f</em>, (the number of cycles that pass through a point) of the wave
Mathematically, we have;


The type of substance that is most likely to contain a covalent bond is ONE THAT IS COMPOSED OF ONLY NON METALS.
Covalent bond is a type of chemical bond in which electron pairs are shared among the participating elements in order to achieve the octet form. Covalent bond is usually found among non metals.
Mass number = protons + neutrons = 34+46 =80
the element with an atomic number of 34 and mass number of 80 is selenium