Answer:
a. certain types of cancers take twenty to thirty years to develop, and cell phone studies have only been monitoring this potential connection for ten years or less.
Explanation:
<u>This statement explains how we can't for the sure claim there are more benefits off the cell phone because the studies of the health effects have not been going on for long enough for us to prove that.</u>
<u>The damage is yet to be revealed, as stated in the claim, but it can be of great influence if proven that cell phones are connected to the development of cancer.</u>
<u>The B statement</u> does not add anything to the first claim and does not contradict it, as it just gives information about phone history usage and not the health benefits or risks.
<u>The C statement </u>is not counterclaiming as it adds up to the mentioned benefits - it explains how cell phones are helping life in general and do not refer to the statement about health risks.
<u>The D statement </u>mentions claims by agencies that are not health-based, and also supports the first statement, saying how there are no links to cancer development so far. It actually only goes with the original statement, and the A statement is counterclaim for it as well.