For a solar eclipse to occur,
a.
the sun must be directly between earth and the moon.
b.
the moon must be directly between earth and the sun.
c.
the moon must be directly behind earth.
d.
earth must be directly between the sun and the moon.

For solar eclipse, Earth, moon and sun should be in perfect alignment with moon in between earth and sun. So option B is correct.

The  grandmother cell  is a hypothetical  neuronthat represents a complex but specific concept or object.[1]  it activates when a person "sees, hears, or otherwise sensibly discriminates"[2]  a specific entity, such as his or her grandmother. the term was in use at least as early as 1966 amongst staff and students in the department of experimental psychology, university of cambridge, england. a similar concept, that of the  gnostic neuron, was proposed two years later