Explanation:

Transgenic techniques involve the transfer of genes from one organism to another to develop desirable traits in the recipient organism. These techniques have been used to solve several agricultural challenges, such as developing crops that are resistant to pests, diseases, and adverse environmental conditions. However, there are some challenges that cannot be solved with transgenic techniques, and one of them is:

D. Public preference for organic vegetables

Organic farming is a method of agriculture that relies on natural inputs and practices to grow crops without the use of synthetic pesticides, fertilizers, or genetically modified organisms. Organic farming is gaining popularity among consumers who are concerned about the safety and sustainability of their food supply. However, transgenic techniques involve the use of genetically modified organisms, which are not allowed in organic farming. Therefore, transgenic techniques cannot be used to develop crops that meet the criteria for organic farming.

Other agricultural challenges that can be solved with transgenic techniques include:

A. Crops are damaged by frost or drought

Transgenic techniques can be used to develop crops that are tolerant to extreme weather conditions such as frost or drought. For example, scientists have developed frost-tolerant strawberries by transferring a gene from a fish that lives in icy waters to the strawberry plant.

B. Crops are damaged by insect pests

Transgenic techniques can be used to develop crops that are resistant to insect pests without the need for synthetic pesticides. For example, scientists have developed Bt cotton, which produces a toxin that is lethal to certain insect pests but harmless to humans and other non-target organisms.

C. Public concern about safety of synthetic pesticides

Transgenic techniques can be used to develop crops that are resistant to pests and diseases, reducing the need for synthetic pesticides. For example, scientists have developed virus-resistant papayas that do not require as many pesticides as conventional papayas.

In conclusion, while transgenic techniques have been used to solve several agricultural challenges, they cannot be used to develop crops that meet the criteria for organic farming due to public preference for natural inputs and practices.