Analyze the sentence to determine the main clause and the subordinate clause. then choose the function of the subordinate clause. it is not right to make a promise unless you are sure you can fulfill the promise. main: a) its not right to make a promise b) its not right to make a promise unless you are sure c) it is not right d) you are sure you can fulfill the promise subordinate: a) unless you are sure you can fulfill the promise b) you are sure you can fulfill the promise c) unless you are sure d) to make a promise unless you are sure you can fulfill the promise subordinate action: a) adverb b) adjective c) noun

Main:
A) its not right to make a promise

Subordinate:
B) you are sure you can fulfill the promise

Subordinate action:
B) Adjective

First, the sentence itself is a clause called the matrix clause (you could also call it a main clause). Within that clause is the main clause "It is not right to make a promise" which contains the subordinate infinitival clause "to make a promise" functioning as complement to the adjective "right".

The matrix clause also contains the subordinate clause "you are sure you can fulfill the promise" which functions as complement to the preposition "unless". Within that clause is a further subordinate clause "you can fulfill the promise" which is a declarative content clause functioning as complement to the adjective "sure".

In some grammars "unless" is treated as a subordinator, not a preposition, in which case the expression "unless you are sure you can fulfill the promise" is a subordinate clause functioning as an adjunct of condition.