Simplify the ratio 6 : 4 by dividing both terms by their highest common factor, which is 2.<br><br>
&bull; 6 ÷ 2 = 3, 4 ÷ 2 = 2<br>
&bull; 6 : 4 = 3 : 2<br><br>
Final Answer: A: 3 : 2