Cardiac muscles of frog are identified under the microscope by the presence of

Explanation

The correct answer is Option A: 'striations and branched fibres.' Cardiac muscle tissue is distinct for its striated appearance and branched fibers, which allow for strong and synchronized contractions. Unlike skeletal muscle, which has striations with unbranched and multinucleated fibers, cardiac muscle fibers are typically branched and contain a single nucleus per cell. Therefore, Options B, C, and D are incorrect due to their inaccurate descriptions of cardiac muscle characteristics.