Match the columns:

Column-$I$	Column-$II$
$(1)$ Lethal mutation	$(a)$ Mutation caused by external factors
$(2)$ Spontaneous mutation	$(b)$ They are metabolic errors
$(3)$ Induced mutation	$(c)$ As a result the mutant dies
$(4)$ Biochemical mutation	$(d)$ Most of the mutations occurring in nature are of this type

(1-C, 2-D, 3-A, 4-B) The correct matches are:
$(1)$ Lethal mutation: $(c)$ As a result the mutant dies.
$(2)$ Spontaneous mutation: $(d)$ Most of the mutations occurring in nature are of this type.
$(3)$ Induced mutation: $(a)$ Mutation caused by external factors (mutagens).
$(4)$ Biochemical mutation: $(b)$ They are metabolic errors that affect specific biochemical pathways.
Therefore,the correct sequence is $(1-c, 2-d, 3-a, 4-b)$.