Final answer:
In the context of turtle graphics, to change the turtle's pensize to 6 pixels, you can use either 'pensize(6)' or 'width(6)'
Step-by-step explanation:
To change the width of the turtle's pensize to 6 pixels in turtle graphics, a popular library for introducing programming to beginners, you should use the command pensize(6) or width(6). Both commands will achieve the desired result. Therefore, options 1 and 2 in your list are correct.