Learn Russian: Девочка пряталась под столом от страха. - The girl was hiding under the table out of fear.

In Russian, от plus the Genitive case is used for involuntary physical or emotional reactions, like acting out of fear, crying from pain, or shaking from cold. You use из for conscious, logical motives, like doing something out of politeness or curiosity. Since fear is an uncontrollable emotion, от страха is the right choice.

Why is the verb пряталась reflexive (ending in -сь)?

The non-reflexive verb прятать means to hide an object, like hiding a present or a book. When a person is hiding themselves, you must use the reflexive form прятаться. Here, the girl is hiding her own body, so we use the past tense feminine reflexive form пряталась.

Why is it под столом (Instrumental case) instead of под стол (Accusative case)?

The preposition под takes the Instrumental case when it describes a static location, answering the question 'where?'. If the sentence were describing her physical movement of getting under the table, answering 'to where?', you would use the Accusative case под стол. Since she is already under the table hiding, we use the Instrumental под столом.

Why use the imperfective verb пряталась instead of the perfective спряталась?