Option 1: The Palk Strait has disputed islands and the Sri Lankan Navy does not allow the ships to cross through.

This option suggests that the reason ships cannot cross through the Palk Strait is because of disputed islands and restrictions imposed by the Sri Lankan Navy. However, this is not the correct answer. While there may be disputes in the area, it is not the main reason ships avoid crossing through the Palk Strait.

Option 2: It is too shallow for ships to cross.

This option is the correct answer. The Palk Strait is indeed too shallow for ships to navigate through. The depth of the strait is not sufficient to accommodate large vessels, making it impractical for ships to cross.

Option 3: Shipping is prohibited through the Strait due to its religious significance connected with the epic Ramayana.

This option suggests that ships are prohibited from crossing through the Palk Strait due to religious significance associated with the epic Ramayana. However, this is not the reason ships avoid the strait. The main reason is the shallow depth.

Option 4: The around Sri Lanka route is actually shorter than crossing through the Palk Strait.

This option suggests that the alternative route around Sri Lanka is actually shorter than crossing through the Palk Strait.