To solve this problem, we need to identify which option represents an example of ex situ conservation.$\newline$Ex situ conservation involves the preservation of components of biological diversity outside their natural habitats.$\newline$Let's analyze each option:$\newline \bullet$Option 1: National park - National parks are protected areas meant for in situ conservation, where ecosystems are preserved in their natural state.$\newline \bullet$Option 2: Seed bank - Seed banks store seeds of various plant species in controlled environments, preserving genetic material outside their natural habitats. This is an example of ex situ conservation.$\newline \bullet$Option 3: Wildlife sanctuary - Wildlife sanctuaries are areas where animals are protected in their natural habitats, representing in situ conservation.$\newline \bullet$Option 4: Sacred grove - Sacred groves are patches of forest preserved due to religious beliefs, also an example of in situ conservation.$\newline$Based on the analysis, the correct answer is Option 2: Seed bank, which is an example of ex situ conservation.