Select the incorrect statement about external fertilization.
A)Organisms showing external fertilization produce a large number of male gametes only
B)External fertilization is very uncertain and requires synchrony between release of male and female gametes
C)It is replaced by internal fertilization in higher organisms as it wastes energy and requires external medium like water
D)It occurs in most of the fishes and amphibians

Hint: External fertilization is a form of reproduction in which a male creature's sperm fertilizes a female individual's egg outside of the female's body. It is dissimilar with internal fertilization, in which sperm are begun by means of insemination and then joined with an egg inside the body of a female organism. External fertilization characteristically occurs in water or a damp area to facilitate the movement of sperm to the egg.

Complete answer:
External fertilization occurs typically in wet environments and needs both the male and the female to release their gametes into their surroundings. A benefit of external fertilization is that it results in the construction of a large number of offspring. One difficulty is that environmental hazards such as predators really reduce the ability of surviving into adulthood. Amphibians and fish, aquatic algae are animals that replicate this way.

When fertilization happens outside the body of the organism, this kind of gametic fusion is known as external fertilization or external syngamy. Organisms exhibiting external fertilization produce a large number of both male and female gametes to improve the chances of fertilization.

Hence, the correct answer is option (A)

Note: In external fertilization sexual selection may not appear to occur during external fertilization, but there are ways it essentially can. The two types of external fertilizers are shell builders and show spawners. For female nest builders, the major choice is the site of where to lay her eggs. A female can decide a nest close to the male she desires to fertilize her eggs, but there is no guarantee that the preferred male will fertilize any of the eggs. Broadcast spawners have a very feeble selection, due to the unpredictability of releasing gametes.