5) That ___, they danced on the sand.

Решение:

В предложении "Last week, we flew to a beautiful island. The weather was hot and sunny. We went swimming with pink dolphins, we ate moon fruit, and in the evening we danced on the beach under the stars." после описания погоды и плавания следует предложение о том, что они делали вечером.

Ответ: in the evening