Is “It is believed the hamburger was invented in Texas” ungrammatical without “that”?

When evaluating the grammatical correctness of a sentence, it's essential to distinguish between facts and assumptions. In this case, the assumption is that omitting "that" would make the sentence ungrammatical. However, a closer examination reveals that the sentence is actually using a construction called a "zero relative clause" or "zero complement." In this construction, the relative pronoun "that" is implied, even if it's not explicitly written. The sentence "It is believed the hamburger was invented in a small town in Texas" is grammatically equivalent to "It is believed that the hamburger was invented in a small town in Texas." The absence of "that" doesn't affect the sentence's meaning or grammatical correctness. In fact, this construction is commonly used in informal writing and speech, particularly in American English. It's often referred to as a "drop the 'that'" construction, as it allows the writer to avoid using a relative pronoun and create a more concise sentence. To illustrate this further, consider the following example: "I think the new policy will be implemented soon" is equivalent to "I think that the new policy will be implemented soon." In both cases, the sentence is grammatically correct, even though "that" is not explicitly written. In conclusion, omitting "that" in the original sentence doesn't make it ungrammatical; rather, it's using a common construction that's widely accepted in informal English usage. So, if you're writing a school test, don't worry about using this construction – just make sure you're clear and concise in your writing.