2. Saturn's atmosphere.hundreds of kilometers deep, is composed mostly of __ a. hydrogen b. methane c. ammonia d. helium

## Step 1<br />The problem is asking us to identify the primary component of Saturn's atmosphere. The options provided are hydrogen, methane, ammonia, and helium.<br />## Step 2<br />Saturn, like other gas giants, has a thick atmosphere composed primarily of hydrogen and helium. The exact composition can vary, but hydrogen is generally the most abundant element in the atmosphere of Saturn.<br />## Step 3<br />Therefore, the correct answer is option a, hydrogen.