Multi-choice problem: Choose from the options at the end, and answer how do you do this: How do you break a dogbane stalk open in order to access the core wood fiber?

OPTIONS:
[A]. Lay the dogbane stalk out on a flat surface. Press your thumb into it to flatten it longitudinally. This will cause the stalk to break in half lengthwise..
[B]. Lay the dogbane stalk out on a flat surface. Press your knee into it to flatten it longitudinally. This will cause the stalk to break in half lengthwise..
[A].