<p>Japan's climate is [similar to the northeastern coast of the United States].</p>
<p>I said [similar to the northeastern coast's climate]
but its [similar to that of the northeastern coast]</p>
<p>WHY?</p>
<p>another q:
according to a leading physicin, the human body's resistance to helpful [as well as] harmful chemicals is the simgnel most importnat problem to be overcome in the fight against cancer.</p>
<p>Your answer is redundant, and repetitive, because “climate” is said twice. “that of” correctly simplifies the statement.</p>
<p>If I was rewriting the second q, I would say something like “resistance to both helpful and harmful.”</p>
<p>1) “That” is a pronoun. “He” is a pronoun. It is better to use a pronoun to substitute a noun than it is to repeat the noun (“Jake ate because he was hungry” as opposed to “Jake ate because Jake was hungry”)</p>
<p>2) “As well as,” taken literally, is like “as big as” or “as intelligent as.” It compares two things that are well to the same degree. One thing can be just as well as another thing, so you may include it. “Helpful” and “harmful” are opposites. One is not as well as the other. It cannot be treated like “and” because the construction is different.</p>