i think i solved it when i used MAX(CASE)

SELECT [STD], 
         MAX(CASE WHEN SUBJECT = 'MATH' THEN MARKS ELSE '' END) MATH,
         MAX(CASE WHEN SUBJECT = 'MATH' THEN COMMENT ELSE '' END) COMMENT,
         MAX(CASE WHEN SUBJECT = 'MATH' THEN TDATE ELSE '' END) TDATE ,
   
         MAX(CASE WHEN SUBJECT = 'ENGLISH' THEN MARKS ELSE '' END) ENGLISH,
         MAX(CASE WHEN SUBJECT = 'ENGLISH' THEN COMMENT ELSE '' END) COMMENT,
         MAX(CASE WHEN SUBJECT = 'ENGLISH' THEN TDATE ELSE '' END) TDATE ,
    
         MAX(CASE WHEN SUBJECT = 'SCIENCE' THEN MARKS ELSE '' END) SCIENCE,
         MAX(CASE WHEN SUBJECT = 'SCIENCE' THEN COMMENT ELSE '' END) COMMENT,
         MAX(CASE WHEN SUBJECT = 'SCIENCE' THEN TDATE ELSE '' END) TDATE 

    FROM [dbo].[EXAM]  GROUP BY STD

Pivots for presentation purposes are not well suited to SQL and often better performed by a "front end" or "reporting tool" despite this, it is possible to pivot this data using T-SQL.

I assume that an unstated requirement is that the columns are presented in a specific left-to-right "block sequence" of "subject-mark-comment-tdate" so there needs to be a way to organize the columns in that sequence. A further probable requirement is that the pivot cater for an unknown number of total columns, for this you need "dynamic sql".

Note: This "unpivot" is complicated by the fact that there are different data types involved, one way to avoid this is to cast all data to strings or sql_variant (which is the approach seen below). Another (that I prefer) is to use JSON explained here but I wasn't also able to control the the "rnk" value as I needed for this query to formulate the numeric sequence of columns.

So, this is proposed:

DECLARE @cols AS NVARCHAR(MAX), @query AS NVARCHAR(MAX);

SELECT @cols = STUFF((SELECT ',' + quotename(concat(c.column_name, cj.rn))
            from INFORMATION_SCHEMA.COLUMNS c
            cross join (
                select row_number() over(order by subject) rn
                from (select distinct subject from exam) e
                ) cj
            WHERE c.TABLE_NAME = 'Exam'
            AND c.column_name <> 'STD'
            order by cj.rn, c.ORDINAL_POSITION
            FOR XML PATH(''), TYPE
            ).value('.', 'NVARCHAR(MAX)') 
        ,1,1,'');

SET @query = 'SELECT STD, ' + @cols + ' 
            from 
            (
                SELECT STD, 
                       concat(COLUMN_NAME,rnk) as COLUMN_NAME, 
                       VALUE
                FROM
                (
                    SELECT STD, 
                           CAST(SUBJECT AS sql_variant) AS SUBJECT, 
                           CAST(MARKS AS sql_variant) AS MARKS, 
                           CAST(COMMENT AS sql_variant) AS COMMENT, 
                           CAST(convert(varchar(10), TDATE ,120) AS sql_variant) AS TDATE,
                           dense_rank() over(partition by STD order by MARKS) as rnk
                    FROM Exam
                ) AS subquery
                UNPIVOT
                (
                    VALUE
                    FOR COLUMN_NAME IN (SUBJECT, MARKS, COMMENT, TDATE)
                ) AS unpvt
            ) x
            pivot 
            (
                max(VALUE)
                for COLUMN_NAME in (' + @cols + ')
            ) p ';

EXECUTE(@query);

see this as a working demo

nb: As I ended up converting the date column into a string to control the format, you could replace the "as sql_variant" with "as varchar(100)"(length of 100 is a guess)