looking for simple subects. we spent most the day picking berries in the woods.

There is only one word in that sentence that is the subject. All the other words make up the predicate. Who is doing the action in the sentence? That's the subject.

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The subject in the sentence "We spent most of the day picking berries in the woods" is "we". To determine the subject, you can ask the question "Who or what is doing the action?" In this case, the answer is "we" because they are the ones doing the action of picking berries. The rest of the words in the sentence, such as "spent," "most of the day," "picking berries," and "in the woods," make up the predicate, which includes the verb and other words that provide information about the subject or the action being performed.