Do you want some ---? Can I have some ---?
Can I have some ______? Sure, ______ yourself. (✓)
Can I have some popcorn? Sure, help yourself.
Can I have some ______? Sure, ______ yourself. (✓)
Can I have some fruit ice pops? Sure, help yourself.
Do you want some ______? No, ______ . (X)
Do you want some crackers? No, thank you. (X)