@Sowmyashree0 Airbnb rules say that you're not allowed to discriminate regarding gender, unless you're in a home sharing type of hosing arrangement where you share spaces with your guests: then you can say that you only host guests of the same gender as you. However, that needs to be clearly laid out in your rules. Unless there is a local law that states that unmarried people of opposite genders cannot share an accommodation, there shouldn't be any reason for refusing their stay.
However... if you're uneasy about it, I'd say you need to make your own decision on it. If the guest made an instant booking, you can cancel up to three guests per year if you feel uncomfortable with the reservation and you won't be penalized. Maybe start by asking the guest some questions about their reason for visiting and what they'll be doing in the area: that might put your mind at ease.