using System;

using System.Collections.Generic;

using System.Linq;

​

public class ScoreInfo

{

    public int Id { get; set; }

    public int StudentId { get; set; }

    public string Subject { get; set; }

    public double Score { get; set; }

​

    public override string ToString() => $"Id: {Id} StudentId: {StudentId} Subject {Subject} Score {Score}";

}

​

public class Program

{

    public static void Main()

    {

         var scoreInfos = new[]

         {

             new ScoreInfo {Id = 1, StudentId = 1, Subject = "GK", Score = 90},

             new ScoreInfo {Id = 2, StudentId = 1, Subject = "PHY", Score = 97},

             new ScoreInfo {Id = 3, StudentId = 1, Subject = "CHE", Score = 89},

             new ScoreInfo {Id = 4, StudentId = 1, Subject = "BIO", Score = 93},

             new ScoreInfo {Id = 5, StudentId = 1, Subject = "TAM", Score = 100},

             new ScoreInfo {Id = 6, StudentId = 1, Subject = "ENG", Score = 95},

             new ScoreInfo {Id = 7, StudentId = 2, Subject = "GK", Score = 85},

             new ScoreInfo {Id = 8, StudentId = 2, Subject = "PHY", Score = 76},

             new ScoreInfo {Id = 9, StudentId = 2, Subject = "CHE", Score = 63},

             new ScoreInfo {Id = 10, StudentId = 2, Subject = "BIO", Score = 79},

             new ScoreInfo {Id = 11, StudentId = 2, Subject = "TAM", Score = 61},

             new ScoreInfo {Id = 12, StudentId = 2, Subject = "ENG", Score = 60}

         };

         var scienceSubjects = new HashSet<string> { "GK", "PHY", "CHE", "BIO" };

​

         var resultQuery = scoreInfos.Select(scoreInfo => new

                                             { 

                                                 ScoreInfo = scoreInfo,

                                                 GrpId = scienceSubjects.Contains(scoreInfo.Subject) ? 0 : 1

                                             })

                                     .OrderByDescending(x => x.GrpId)

                                     .ThenByDescending(x => x.ScoreInfo.Score)

                                     .Select(x => x.ScoreInfo)

                                     .Take(5);

        foreach(var scoreInfo in resultQuery)

        {

            Console.WriteLine(scoreInfo);

        }

    }

}