The true statement about the main idea of a text is that identifying the main idea of a text can help you understand what you read. Option A is correct.
When a reader indetify the main idea, he/she will be able to understand all the details and the explanations developed thoroughout the entire text. In addotion to this, the details are always meant to support the main idea. The main idea can be supported by expert, especially if the writer is not an expert on the subject. It is also important to be aware that main idea is not always directly stated in narrative text, and that sometimes we have to figure it out by reading between the lines.