An underground surveyor can distinguish coloured route labels under bright lamps. After several minutes in very dim light, the surveyor cannot detect pale obstacles. The cornea, lens and optic nerve are healthy.
Which conclusion about the surveyor's rod cells and cone cells is most likely?
The rod cells do not function normally; the cone cells function normally.
The rod cells and cone cells both function normally.
The rod cells function normally; the cone cells do not function normally.
Neither the rod cells nor the cone cells function normally.
102 exam-style questions on Edexcel GCSE Biology 2.4 The eye, covering 2.4.1 Structure and function of the eye and 2.4.2 Eye defects and their correction. Each one has a worked solution and a mark scheme showing where the marks go.