Final answer:
DDR3 is the most commonly used type of RAM in today's lower-end computers because of its cost-effectiveness and compatibility with older systems.
Step-by-step explanation:
The type of RAM memory used most often in today's lower-end computers is b) DDR3. DDR3 stands for Double Data Rate Type 3 and has been the standard for RAM in computers for many years. Though DDR4 has been available since 2014 and offers higher performance, DDR3 is still widely used in budget and lower-end systems due to its cost-effectiveness and compatibility with older motherboards. It's important to note that as technology advances, the preference for RAM types in new systems is leaning towards DDR4 and the upcoming DDR5.