To complete the text with the present simple form of the verbs, you need to consider the subject of each sentence and apply the appropriate verb form. Here's the completed text:
What is an eclipse?
A solar eclipse happens when the moon passes in front of the sun. This only takes place when there is a new moon. It lasts for up to 7.5 minutes. During a solar eclipse, it is dark. The birds do not sing, and animals keep still and quiet. A solar eclipse does not happen very often, and most people enjoy seeing one. However, it's important not to look straight at the sun. If you do not remember this, you can damage your eyes.
A lunar eclipse occurs when the earth's shadow falls on the moon. The moon looks dim until it comes out from the shadow.
Explanation:
happens, passes, takes, lasts: These verbs are in the third-person singular form because the subjects (e.g., "A solar eclipse," "the moon," "This," "It") are third-person singular.
do not sing, keep, does not happen, enjoy: "Do not sing" and "does not happen" are negative forms. For the third-person singular, "does not" is used (e.g., "does not happen"). For plural subjects (e.g., "birds" and "people"), use "do not" (e.g., "do not sing," "enjoy"). "Keep" is in the base form because it follows modal-like usage for general truth.
do not remember: In this case, "you" is the subject, which is second-person, so "do not" is used.
occurs, falls, looks, comes: These verbs are also in the third-person singular form, following the same rule as above, since the subjects (e.g., "A lunar eclipse," "the earth's shadow," "The moon") are third-person singular.
