<p>The large beech trees in my (neighbors') yards always shed (their) dark red leaves late (in the fall) (when) the other trees are bare. The answer is no error. Shouldn't it be its instead of their? Can you use "their" with non-humans?</p>
<p>(At age fifteen) Martha observed chemists doing experiments (in a lab) and knew immediately (that) she would like to be (one). I thought the answer was "At age fifteen" but it is "one". Can someone tell me why?</p>
<ol>
<li><p>Yes, their is simply the plural possessive of “they,” which, likewise, can have non-humans as an antecedent. Take this sentence for example: “I love these shoes because they always feel comfortable, even after soaking in the rain.”</p></li>
<li><p>The sentence says that Martha observed “chemists” and immediately knew she would like to be one. Therefore, one, a singular pronoun in this case, is referring to “chemists,” a plural antecedent.</p></li>
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