________ their luggage, the tourists hurried to the airport． Packed。 After packed。 Having packed。 Packing。
The development of the light bulb ________partly as a result of the widespread availability of electricity and the need for cheap, clean light． occurring。 was occurring。 was occurred。 occurred。
How can he do so much work? He ________ stay late at the office every evening and take work home at weekends． need。 can。 might。 must。
What we have to take________the courses offered only for this term．
