Question: To permanently remove empty lines from a file called textfile, which command could you use?

1. `sed -i '/^$/d' textfile`
2. `sed '/^$/d' textfile`
3. `cat textfile | sed '/^$/d`
4. `sed -i 's/^$//' textfile`

Answer: The correct answer of the above question is Option A:`sed -i '/^$/d' textfile`