The correct option is
C a is a fact, b and c are opinions.
The correct answer is Option A.
In the given sentence we are to identify which sentence is a fact and which is an opinion.
So we first define fact and opinion.
A fact is something that is proved to be true. It can be used as an evidence. For e.g. There are 7 continents in the world- this is a fact since it is proven.
An opinion is a view or a judgment that is not necessarily based on evidence or knowledge. It cannot be used as evidence since it is not proven.
For e.g. The Indian government should take steps to protect the environment.
So we apply these definitions to the given sentences in the question.
Sentence A- India is the only country other than USA and Japan, to have built a supercomputer indigenously.
This sentence is based on established knowledge and is proved and therefore it is a fact.
Sentence B- Korea may have also built the supercomputer indigenously.
This sentence contains the word 'may' - This means that this sentence is not based on established knowledge and is not proven. Therefore this sentence is an opinion.
Sentence C-Germany may also have the built the supercomputer indigenously.
This sentence also uses the word 'may' - This means that this sentence is not based on established knowledge and is not proven. Therefore this sentence is an opinion.
Hence sentence A is a fact and sentence B and C are opinions.
The other options B, C, and D do not comply with the definitions of fact and opinion.
Thus option A is the correct answer.