Answer:
H2 + I2 → 2 HI.
Explanation:
Hydrogen iodide is a diatomic gas which can be readily formed from the direct combination of the elements involved which is hydrogen and iodine. Both elements can be combined by irradiating the mixture with an electromagnetic radiation that has a wavelength which is equal to that needed to break the iodine molecule bond between the two iodine atoms 
 
        
             
        
        
        
During the Physical changes
        
             
        
        
        
The correct answer is Crystals.
Unlike sugar, salt is not made out of crystals, but both salt and sugar are made out of atoms, that is molecules, and can have ions.
        
             
        
        
        
Answer: Option (d) is the correct answer.
Explanation:
The amount of salt present or dissolved in water or water body is known as salinity.
When salinity increases then number of particles increases, therefore, density will increase. Also, number of ions will decrease thus, electrical conductivity will decrease.
On the other hand, increase in salinity will increase the amount of salt (NaCl) is the water.
Thus, we can conclude that out of the given options, the option all of the above is true.