Triangle ABC is drawn inside a circle such that AB is a diameter. Which statement best explains why ∠ACB is a right angle?
(a) The angle subtended by any chord at the centre is half the angle subtended at the circumference.
(b) Because the angle subtended by chord AB at the centre is 90∘, the angle at the circumference is 45∘.
(c) A diameter subtends a right angle at the circumference because it subtends an angle of 180∘ at the centre.
(d) Equal chords in a circle subtend equal angles at the centre, so AB being the longest chord produces a right angle at C.}],