Which is correct way to define featuresX = df['clo1', 'col2', . . .]X = df[[clo1, col2, . . .]]X = df[['clo1', 'col2', . . .]]X = df[clo1, col2, . . .]

To determine the correct way to define a selection of multiple columns from a DataFrame in pandas, we should closely analyze the syntax.

1. ### Correct Syntax for Column Selection

The correct method to select multiple columns in pandas involves using double square brackets while passing a list of column names as strings. The correct format is:

• df[['col1', 'col2', ...]]

2. ### Breakdown of Each Option

1. X = df['clo1', 'col2', ...]: Incorrect. This syntax does not properly define a list of columns; it is attempting to index with a tuple.
2. X = df[[clo1, col2, ...]]: Incorrect if clo1 and col2 are not defined as variables. You need to use string literals.
3. X = df[['clo1', 'col2', ...]]: Correct. This is the appropriate way to select multiple columns as it uses a list of strings.
4. X = df[clo1, col2, ...]: Incorrect. Similar to option one, this treats the arguments as tuple indexing, which is invalid.

Final Answer

The correct way to define multiple columns in a DataFrame is:

• X = df[['col1', 'col2', ...]]