Answer :
"The executive branch mainly enforces federal laws" is not correct. The Executive Branch can choose to not respect certain laws and veto bills, but this is not its main task.
The NOT true statement = "The Executive branch mainly interprets the federal laws and upholds or negates them." That statement describes the Judicial branch, headed by the US Supreme Court.
The other statements all are pertinent to the Executive branch of government. The Justice Department is part of the Executive branch, thus responsible for enforcement of laws. The 15 divisions of the Executive branch are the various departments headed by Cabinet level officials -- such as the Department of Defense, Department of Education, etc.
One statement wasn't included in the list of Executive branch which maybe should be listed as a key responsibility of the chief of state, the President: Article II of the US Constitution names the President the Commander-in-Chief, so the Executive branch is in charge of the US Armed Forces. The War Powers Act (1973) asserts that Congress must give approval for continued deployment of any US troops. But the President has the authority to send American forces into combat prior to getting such approval for their continued military action from Congress.