The correct answer is the second option. During fusion, uranium atoms are fused together. Fusion reaction happens when two or more nuclei combine or collide to form an element with a higher atomic number. In this process, some of the matter of the fusing nuclei is converted to energy.
The answer for four is frequency.
Due to hydrogen bonding there is a formation of cage like structure called lattice in ice due to which <span> density of ice is less than that of water. Moreover, it is a known fact that density of water is maximum at 4°C.</span>