Explanation
The correct answer is (d) could be.
1. Context Analysis:
The first sentence, "I don't know where Maya is," clearly indicates uncertainty. The speaker is making a guess about Maya's current location.
2. Why "could be" is the correct choice:
In English, we use could, may, or might to express a possibility in the present when we are not sure about the facts.
3. Why the other options are incorrect:
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(a) would be: This is typically used for hypothetical situations (if something else were true) or to describe a predictable behavior, which doesn't fit the "I don't know" context here.
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(b) is: This expresses a 100% certainty. If the speaker says "I don't know," they cannot follow it with a definite statement like "She is at home."
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(c) can be: While "can" expresses general ability or general possibility (e.g., "It can be cold in December"), we specifically use could for a specific possibility in the present moment.
Grammar Formula for Present Possibility
To express a guess or an uncertain fact about the present, use the following structure:
Subject+could / may / might+be+Complement
Key Rule: When you are uncertain, Could functions as a weaker version of "maybe," fitting perfectly with the phrase "I don't know."
