Marsupials are a group of mammals that give birth to their young ones early in their development, who then continue to grow in an external pouch on the mother`s body.

Option 1: Lower Cretaceous: This period is associated with the first appearance of the marsupials. It is part of the Cretaceous Period that occurred approximately 145 to 100 million years ago. The first true marsupials appeared during this period.

Option 2: Upper Cretaceous: Marsupials were already present during this period, which means they appeared before the Upper Cretaceous. This disqualifies this option.

Option 3: Early Jurassic: This option is incorrect because marsupials didn`t appear this early. The Jurassic period predates the Cretaceous and is known for the domination of dinosaurs.

Option 4: Middle Jurassic: This option is also incorrect, for the same reason as Option 3. Marsupials didn`t appear this early.

Hence, the correct choice is Option 1: Lower Cretaceous.