<p>Your last example:</p>
<p>If asked to name a musical group with broad and lasting appeal, many people would choose the Beatles.</p>
<p>is very much a sentence.</p>
<p>There is an implicit part to the first clause. I’ll put it in brackets:</p>
<p>If [they are] asked to name a musical group with broad and lasting appeal, many people would choose the Beatles.</p>
<p>Again, I’m not sure of the context of the rule you mention. I don’t think it is generally valid. There are situations in English where words are implied, such as the “they are” above.</p>
<p>Quite apart from your clause versus sentence question your first example in post #6:</p>
<p>“If asked to name a musical group with broad and lasting appeal, the Beatles would be the choice for many, no matter what kinds of music are actually preferred.”</p>
<p>is grammatically flawed, so it’s hard for me to take it seriously. The antecedent of the implied pronoun (after “if”) is ambiguous. But rearranging the sentence a bit to remove all ambiguities you have:</p>
<p>“When [they are] asked to name a musical group with broad and lasting appeal, most people, no matter what kind of music they actually prefer, would choose the Beatles.”</p>
<p>Your final proposed sentence</p>
<p>“By building houses, the USA can reduce carbon emissions, in the sea, the USA can help the planet.”</p>
<p>has multiple grammatical problems unrelated to your question so again it is hard for me to take it seriously. I actually don’t even understand what it means. What’s worse is that it seems like two unrelated sentences tied together with a comma splice.</p>
<p>Anyway perhaps your rule would work in some situations if you take into account the implicit pronouns in one or the other clause. English is a complex language with many rules, idioms and exceptions. The SAT rarely tests the boundaries of the language.</p>