Explanation:

The correct option is 3 (both (a) & (b)).

Section 45 of the Indian Evidence Act, 1872 allows the opinion of an expert to be considered in matters such as the identity of handwriting and identity of finger impressions. This section permits experts in fields like handwriting analysis or forensic science to provide their opinion on these matters, which may be used as evidence in court. The expert’s opinion is based on their specialized knowledge and expertise, and it can be crucial in resolving disputes related to the authenticity of documents or identification in criminal cases.