The correct answer is option 4, which states that Kalidasa wrote the Vasavadatta.

Option 1 pairs Somadeva with Kathasaritsagara. This is a correct match as Somadeva is indeed the author of the Kathasaritsagara, a famous collection of stories.

Option 2 pairs Ashvaghosha with Buddhacharita. This is also a correct match as Ashvaghosha is the author of the Buddhacharita, which is a biographical poem about the life of Gautam Buddha.

Option 3 pairs Bilhana with Vikramankadeva-charita. This is another correct match as Bilhana is the author of the Vikramankadeva-charita, an epic poem that depicts the life of King Vikramaditya.

Therefore, the only pair that is not correctly matched is option 4, where Kalidasa is stated to be the author of Vasavadatta. Alert - The correct answer should be Vasubandhu instead of Kalidasa, who wrote the highly influential Buddhist text, the Abhidharmakosa.