Rocky mountain juniper (juniperus scopulorum) and one-seeded juniper (j. monosperma) have overlapping ranges. if pollen grains (which contain sperm cells) from one species are unable to germinate and make pollen tubes on female ovules (which contain egg cells) of the other species, then which of these terms is applicable? a) behavioral isolationb) mechanical isolationc) hybrid breakdownd) reduced hybrid viability

Option B, Mechanical Isolation

Explanation:

Mechanical isolation is a phenomena which prevent species from mating each other.

In mechanical isolation,  species have different physical structure due to which they are unable to interbreed.

For example - In snails, two certain species are unable to mate as the shell of one is coiled in the same direction as that of shell of other. Hence, two right coiled snails  cannot breed with each other. The same applies to the left side tailed species.

Hence, option B is correct

the answer would be 2, if crossing over doesn’t occur 2 out of 4 of the daughter cells will have that allele.

hope this : )