One thing should be immediately clear: this is an appositive question. 'Team leader' is in apposition with 'Riley Crane'. If you don't known what an appositive is, you'll find all you need to know in our appositive post.
Knowing that this question is checking you on your understanding of appositives already eliminates two options. The only thing we try to understand when dealing with appositives is whether the appositive is essential or on-essential, i.e. whether or not it will need commas. Since the only choice we have is two commas or no commas, option H and J can easily be eliminated. You'll only seriously think about them if you don't know that this question is about appositives. Good proof that understanding what a question asks about is very powerful in simplifying the process of eliminating wrong options.
Now, is this appositive essential or not? The phrase 'team leader' might seem to exclude all other options and therefore make the following appositive non-essential. This impression is increased if we have a look at the previous sentence, where it is said that the team was from the MIT. So it appears to be clear that there can only be one team leader, and that there can be only one team meant here. But, in fact, the correct answer is G. The appositive here is essential. Why? This seems to go against the rules!
No it doesn't. The reason is simple: there is no definite article. The absence of the article reduces the phrase's specificity and thus makes the appositive essential. In case the initial phrase was 'the team leader', the appositive would be non-essential. It would be clear that one grammatically very specific leader is meant (marked by the use of the definite article).
When dealing with appositive questions on the ACT English test, watch out for the definite article. Very general phrases like 'Italian writer' or 'Jazz trumpeter' will be followed by essential appositives. A general phrase, even if it might be quite specific in the context, can only be followed by a non-essential appositive if the phrase has a definite article.
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