**Option A **
Let us take an extreme case when we have a nucleus of mass no. 99 and another nucleus of same mass no. 99. Now when these nuclei fuse they give a new nucleus of mass no. 198.
Now according to graph nucleus with mass no. 198 has binding energy greater than the parent nuclei. So fusion of nuclei betweenmass of 51 to 100 will release energy as they achieve greater stability.
**Option B **
Nuclei with mass no. between 200 to 260, when get broken into two daughter nuclei, will give nuclei with mass no < 200 (always). And nuclei with mass no between 100 to 200 have higher binding energy in the graph. So fission of nuclei with mass no between 200 to 260 will release energy as they achieve greater stability.