Right choice is (a) 1.5 – 3 Tesla
To explain: MRI’s have three major portions which work together to form an image. The largest portion is taken up by the magnet. This magnet is always on and produces a Magnetic Field of the strength of 1.5 – 3 Tesla. Commercially, 1.5 – 2 T was used but now even with 3T have been introduced. For research purposes, MRI of 7T has also been constructed.