It is a covalent bond. Whenever a compound uses such suffixes like mono, di, tri, tetra, and so on, it is a covalent compound- thus having covalent bonds.
Answer :
- Nuclear fission : In nuclear reaction, the nucleus of a larger atom breaks into two or more smaller nuclei. In fission process, protons and neutrons are produced and larger amount of energy is released.
Example : In nuclear power plant, the energy released from the process of nuclear fission which is converted into electrical energy that is used in our homes and factories.
- Nuclear fusion : In nuclear reaction, the nuclei of two or more smaller atoms combine together to form single larger molecule. In fusion process, the mass of the resulting nuclei is more as compared to the starting nuclei and large amount of energy is also released.
Example : This process occurs in the sun and stars. In this, the isotopes of Hydrogen, Tritium and Deuterium combine together to form a neutron and a helium atom under high pressure and temperature.
The given reaction is,

In this reaction, the positive and negative ions of both the reactants rearrange resulting in the formation of new compounds. Such a reaction is referred to as the double replacement or the double displacement reaction. These type of reactions usually take place in aqueous medium and one of the products is a precipitate.
Double displacement reactions are of three types, precipitation reaction, neutralization reaction and reaction involving the formation of a gas. The given reaction is a precipitation reaction as one of the products is a solid.
Choice A is the correct one