The eclipse of the sun occurs when the

Analyze the question: It asks about a solar eclipse (eclipse of the sun), so we need to find the arrangement of the sun, moon and earth that blocks sunlight from reaching part of the earth.

Concept:

• Solar eclipse: The moon passes between the sun and the earth. The moon blocks sunlight and casts a shadow on the earth. This happens at new moon.
• Lunar eclipse: The earth passes between the sun and the moon. The earth's shadow falls on the moon. This happens at full moon.

Step-by-step evaluation of the options:

• A. Moon is between the sun and the earth. Sun, moon, earth lie roughly in a straight line, with the moon in the middle. This is the basic condition for a solar eclipse. ✔
• B. Earth is between the sun and the moon. This describes a lunar eclipse. ✘
• C. Moon is not completely hidden in the earth's shadow. This describes a partial lunar eclipse. ✘
• D. Moon's umbra falls on some part of the earth. This is true of a total solar eclipse, since the umbra reaches the earth in those places. However, it is a consequence of the alignment, not the general condition, and it only describes a total eclipse. Partial eclipses (penumbra only) also count as solar eclipses. So A is the better and more complete answer. ✘

Answer: The eclipse of the sun occurs when the moon is between the sun and the earth, which is option A.

Tip: Remember "Solar = Moon in the middle" and "Lunar = Earth in the middle". The object in the middle is the one that casts the shadow. Also, the name tells you which body is darkened: in a solar eclipse the sun is blocked from our view, and in a lunar eclipse the moon is darkened.