Given a pandas dataframe, df, as follows:

	open		high	low	close	volume
2021-11-15	1017.63		1031.9800	978.60	1013.39	34775649
2021-11-16	1003.31		1057.1999	1002.18	1054.73	26542359
2021-11-17	1063.51		1119.6400	1055.50	1089.01	31445365
2021-11-18	1106.55		1112.0000	1075.02	1096.38	20898930
2021-11-19	1098.87		1138.7199	1092.70	1137.06	21642258

How would you keep only two columns from the dataframe?

	a.	df=df['date', 'close']
	b.	df=df[['date', 'close']]
	c.	index.set_names(['date', 'open'])
	d.	Index(['date', 'open'])