The correct answer is (c) 20 votes.
The Manmohan Singh government won the vote of confidence in the Lok Sabha on 22 July 2008 by a margin of 20 votes. The government had the support of 275 members of the Lok Sabha, while the opposition had the support of 255 members. The remaining 10 members were either independent or did not vote.
The vote of confidence was held after the government had lost the support of the Left Front, which had been a key ally of the government. The Left Front had withdrawn its support from the government over the issue of the Indo-US nuclear deal.
The government was able to win the vote of confidence with the support of the Samajwadi Party and the Rashtriya Janata Dal. The two parties had earlier been part of the opposition, but they had decided to support the government in the vote of confidence.
The vote of confidence was a major victory for the Manmohan Singh government. It showed that the government had the support of the majority of the members of the Lok Sabha. The vote of confidence also helped to stabilize the government and to ensure that it would be able to continue to function effectively.
The options (a), (b), and (d) are incorrect because they are not the correct margin by which the Manmohan Singh government won the vote of confidence in the Lok Sabha on 22 July 2008.