Hi,
Are these responding sentences correct? Are the prepositions 'by' and 'on' necessary? Of all four, I am most comfortable with no.1 and 2.
Q: John, can I get/prepare you something to eat?
A: 1. No, I will get/prepare it by myself.
2. No, I will get/prepare it on my own.
3. No, I will buy/prepare it myself.
4. No, I will buy/prepare myself.