Crossing of F1 with recessive parent is

Answer: Option B

Option A: Back cross
This is a general term.
It means crossing a hybrid (like our F1) with *any* of its parents (dominant *or* recessive).

Option B: Test cross
This is the correct answer.
A test cross *specifically* means crossing the F1 hybrid with the recessive parent.
It's used to figure out the genotype of the F1.

Option C: Monohybrid cross
This refers to the type of cross, not the specific breeding pattern.
It means crossing individuals to study the inheritance of *one* trait only.

Option D: Single cross
This generally refers to a cross between two inbred lines.
It's not directly related to crossing an F1 with a recessive parent.

Therefore, the best answer is B: Test cross.