What happened as a result of the us invasion of iraq in 2003:
saddam hussein was convicted of war crimes and executed.
iraq gave up the al-qaeda members it had been harboring.
many countries joined the invasion and secure peace in iraq.
osama bin laden was forced into hiding and left al-qaeda weakened

The correct answer is:

Saddam Hussein was convicted of war crimes and executed.

In regard to answer C - many countries did NOT join the US effort in Iraq the way they had back in the Gulf War of 1991.  It was primarily a US initiative this time.

In regard to answer D about Osama bin Laden -- that happened after US military action against AFGHANISTAN (not Iraq).

The war in Afghanistan, begun in 2001, was aimed against the al-Qaeda terror group that was based in Afghanistan and had perpetrated the 9-11 attacks against the United States.  It also aimed to removed the Taliban government from power in Afghanistan, a government which had harbored al-Qaeda and was itself seen as an illegitimate power.

The war in Iraq was pursued beginning in 2003 as a preemptive strike against the regime of Saddam Hussein and the perception that he had stockpiles of weapons of mass destruction that could be used for terroristic purposes.  That perception did not turn out to be a full reality, but the war pursued regime change in Iraq nonetheless.  Saddam Hussein was removed from power.  Later, in 2006, Hussein was convicted of crimes against humanity by the Iraqi Special Tribunal.  He was executed by hanging.  

the answer is a, salt plain