A. Create the opportunity and check the opportunity. recordtype, which will have the record ID of the current user's default record type, before inserting.

B. Query the Profile where the ID equals userinfo.getprofileID () and then use the profile opportunity.
getdefaultresoratype (} method,

C. Use the schema. Userinfo. Opportunity. getDefaultRecordType {) method.

D. Use opportunity. sobjectTyps. getDeacribse().getRecordTypeInfos {) to get a list of record types, and iterate through them until isDefaultRecordtypeMapping {) is true.