The dengue fever is caused by the bite of which of the following mosquitoes?

1. A

   Asian tiger mosquito

   Option (a) mentions the Asian tiger mosquito, which is a species of Aedes (Aedes albopictus). While it can transmit dengue, it is not the primary genus-level answer expected in standard classification questions.

2. B

   Aedes

   Option (b) states that dengue fever is transmitted by Aedes mosquitoes, specifically Aedes aegypti. This genus is the primary vector for several arboviruses including dengue, chikungunya, and Zika, making this the correct and most encompassing choice.

3. C

   Culex

   Option (c) names Culex, a genus known for transmitting West Nile virus, Japanese encephalitis, and lymphatic filariasis. It is not the principal vector responsible for spreading dengue fever.

4. D

   Anopheles

   Option (d) refers to Anopheles, the mosquito genus responsible for transmitting malaria parasites. It has no role in the transmission of the dengue virus.

Summary. Official key is (b) because Aedes mosquitoes are the primary vectors for the transmission of the dengue virus globally. Other genera such as Anopheles and Culex are responsible for different vector-borne diseases like malaria and Japanese encephalitis respectively. Although the Asian tiger mosquito in option (a) belongs to the Aedes genus, 'Aedes' provides the precise taxonomic level required by the question. Therefore, option (b) is the accurate and complete answer.