The answer is "Rising and expanding air or atmosphere cooling".
To form a cloud the air must be cooled to the temperature of dew point. when there is expansion of air, it cools to the dew point and thus the formation of cloud happens. This process is very common and used for the formation of clouds.
The electron geometry of TeCl6 is octahedral, while the molecular geometry is octahedral, non polar.
Octahedral geometry or six electron pairs is the basic geometry for a molecule containing a central atom with six pairs of electrons, such as TeCl6 or SF6. As we replace bonding pairs with non bonding pairs the molecular geometry changes to square pyramidal to square planar.
Number of moles is defined as the ratio of given mass in g to the molar mass.
The mathematical formula is:
Number of moles = 
(1)
Number of zinc atoms is equal to 
, by Avogadro number, number of moles can be calculated.
As, 1 mol=
atoms, hence,
= 0.2822 mol
Now, from formula (1), calculate mass in g (molar mass of zinc = 65.4 g/mol)
0.2822 mol = 
mass in g = 
= 18.45588 g
Thus, by rounding off the above number, it will come near about 19 g approximately.
Hence, option (C) is the correct answer.
Methane is lighter than air, having a specific gravity of 0.554. It is only slightly soluble in water. It burns readily in air, forming carbon dioxide
and water vapour; the flame is pale, slightly luminous, and very hot.
The boiling point of methane is −162 °C (−259.6 °F) and the melting
point is −182.5 °C (−296.5 °F). Methane in general is very stable, but
mixtures of methane and air, with the methane content between 5 and 14
percent by volume, are explosive. Explosions of such mixtures have been
frequent in coal mines and collieries and have been the cause of many
mine disasters.
