Among the linguistic occurrences that most students claim to complain about doubts are the subordinate clauses, given the different classifications, complexity of rules, in short, attributes that are peculiar to the language we speak.
However, in addition to such aspects, it is equivalent to affirming that the similarities existing between these sentences, in dealing with the classifications we attribute to them, they also represent punctual cases in these inevitable questions. As a result, we reserve the right to bring you some information that can certainly make a difference in your understanding of this “dreaded” learning. So, let's go to the examples:
Some students stated that they had not done the assignment.
When we stick to the classification that could be attributed to such a statement, knowledge indicates that:
Some students declared - main prayer
That they had not done the task - direct objective substantive subordinate clause.
We infer that the integral conjunction “that” is the main element that leads us to this classification. Then, if we analyze it better, we find that the main clause consists of a declared subject, explicit, now demarcated by "some students", where "students" represents the center of the greater meaning, the core.
In this sense, supported by the idea that the subject is explained, we can say that it is a direct objective noun subordinate clause.
Let's go to another example:
It was declared that the task would not be done.
Sorting, we have to:
main prayer - declared himself
Subjective substantive subordinate clause – that the task was not going to be done.
Transforming this prayer to the passive analytic voice, we have:
It was declared that the task was not going to be done.
When we analyze, we notice that the main clause is given by “it was declared”.
Regarding, therefore, these elucidations, it is equivalent to affirming that it is a question of subjective subordinate clause, given that the subject is not contained in it.
Source: Brazil School - https://brasilescola.uol.com.br/gramatica/diferencas-entre-subordinada-subjetiva-objetiva-direta.htm