cara mengubah kalimat direct speech menjadi indirect speech

Changed direct speech into indirect speech

a.       If only the statement of direct speech is present tense we have to change becomes simple past tense. 
b.      If only the statement of direct speech is present continuous we have to change becomes a past continuous 
c.       If only the statement of direct speech is present perfect we have to change becomes a past perfect  
d.      And if only the statement of direct speech is simple past tense we have change becomes the past perfact.