The correct answer is (a). Representative Suit Order 1 Rule 8 is necessary.
Representative Suit Order 1 Rule 8 is a rule of the High Court of Judicature at Bombay that allows a person to file a suit on behalf of a group of people who have suffered the same injury. In this case, the person who has filed the suit is claiming that their right to use a public street has been affected by encroachment. This is an injury that affects a group of people, as all members of the public have the right to use public streets. Therefore, the person who has filed the suit can file a representative suit on behalf of all members of the public who have been affected by the encroachment.
The other options are not correct. Option (b) is incorrect because Representative Suit Order 1 Rule 8 is necessary in this case. Option (c) is incorrect because writ jurisdiction is not the appropriate remedy for this type of claim. Option (d) is incorrect because this is a situation where Representative Suit Order 1 Rule 8 is necessary.