In the UK, a Civil Partnership is only between same-sex partners. Even though same-sex couples can (now) legally marry, they can also form a civil partnership (precursor to legal marriage), which opposite-sex couples can't. This is more info than you asked for...
If you are already married and you (the applicant) are the husband, select Husband.
If you are already married and you (the applicant) are the husband, select Husband.