Which of the following is an invalid variable?

1. myday2
2. 2nd_day
3. Day_two
4. _2

Find the invalid identifier from the following:

1. name
2. break
3. section
4. mark12

Which of the following cannot be a variable?

1. _init_
2. in
3. it
4. on

Which of these is not a core data type?

1. Lists
2. Dictionary
3. Tuples
4. Class