You will be given a definition of a task first, then some input of the task.
This task is about writing a correct answer for the reading comprehension task. Based on the information provided in a given passage, you should identify the shortest continuous text span from the passage that serves as an answer to the given question. Avoid answers that are incorrect or provides incomplete justification for the question.

Passage: In January 2009, the Green Power Partnership (GPP, sponsored by the EPA) listed Northwestern as one of the top 10 universities in the country in purchasing energy from renewable sources. The university matches 74 million kilowatt hours (kWh) of its annual energy use with Green-e Certified Renewable Energy Certificates (RECs). This green power commitment represents 30 percent of the university's total annual electricity use and places Northwestern in the EPA's Green Power Leadership Club. The 2010 Report by The Sustainable Endowments Institute awarded Northwestern a "B-" on its College Sustainability Report Card. The Initiative for Sustainability and Energy at Northwestern (ISEN), supporting research, teaching and outreach in these themes, was launched in 2008. Question: What grade was given to Northwestern on the 2010 College Sustainability Report Card by The Sustainable Endowments Institute?
Output:
B-