A.Good marks were seldom being obtained by those who worked hard.
B.Good marks are seldom obtained by those who worked hard
C.Seldom had good marks been obtained by those who worked hard
D.Good marks were seldom obtained by those who worked hard
Answer: D
The tense of the sentence is not past/present perfect or past/present continuous ‘been’ and ‘being’ cannot be used. The sentence is in past tense so option (d) is the most apt choice