The correct answer is A. trip.
A trip is a journey to a place outside of one’s usual environment for a short period of time, typically for pleasure. A picnic is a meal eaten outdoors, typically outdoors in a park or on a beach. A visit is a short stay in a place, especially one made to see someone or something. A tournament is a series of contests between a number of competitors, typically involving a number of games or matches played to determine the winner.
In the given question, the school took the students on a three-day excursion to Goa. This is a clear example of a trip, as it is a journey to a place outside of the students’ usual environment for a short period of time, typically for pleasure. The other options are not correct, as they do not describe the situation in the question. A picnic is a meal eaten outdoors, typically outdoors in a park or on a beach. A visit is a short stay in a place, especially one made to see someone or something. A tournament is a series of contests between a number of competitors, typically involving a number of games or matches played to determine the winner.