Part c during an annular solar eclipse. dthe moon is closer to earth than usual earth is too far away from the sun for the entire sun to be blocked the moon is too far away from earth to block the entire sun the observer watching the eclipse is in the umbra of the moon's shadow

The Short
The Sun is completely blocked in a solar eclipse because the Moon passes between Earth and the Sun. Even though the Moon is much smaller than the Sun, because it is just the right distance away from Earth, the Moon can fully blocks the Sun's light from Earth's perspective.

Just do the math, then think