What is a large topic of consternation among American?

Choices:
A. recent immigration
B. not enough information
C. policy speeches
D. terrorism
terrorism
WASHINGTON — Democratic presidential front-runner Hillary Clinton called Republican rival Donald Trump dangerous and unqualified for the presidency in a blistering foreign policy speech Thursday in San Diego, California.
"He is temperamentally unfit to hold an office that requires knowledge, stability and immense responsibility," Clinton said. "This is not someone who should ever have the nuclear codes."
Trump “doesn’t understand America, or the world,” she said. "It’s not hard to imagine Donald Trump leading us into a war just because somebody got under his very thin skin."
In anticipation of the address, Trump attacked his Democratic opponent on Twitter. “Crooked Hillary Clinton, who I would love to call Lyin’ Hillary, is getting ready to totally misrepresent my foreign policy positions,” he tweeted.
Clinton emphasized her own experience as first lady, senator and secretary of state, saying she would provide the steady diplomacy the country needs.
“National security is the foundation of how we make sure our interests are pursued in the world,” said Louis Goodman, Emeritus Dean of International Relations at American University in an interview with VOA.
With polls show terrorism is a major concern among Americans, Clinton targeted Trump's positions on the issue.
Trump, the presumptive Republican presidential nominee, has promised to temporarily block Muslims from crossing U.S. borders.
"The struggle against radical Islam also takes place in our homeland. There are scores of recent migrants inside our borders charged with terrorism. For every case known to the public, there are dozens more. We must stop importing extremism through senseless immigration policies," Trump said in a foreign policy speech in April.
Trump's other anti-terrorism proposals include a pledge to torture and murder the families of suspected terrorists and target Islamic State.
"I have a simple message for them," Trump said. "Their days are numbered. I won't tell them where and I won't tell them how. But they will be gone. And soon."
But Clinton said Trump's presidency would have the opposite effect.
“A Trump presidency would embolden ISIS,” she said referring to the group also known as Islamic State.
The two presidential candidates have presented very different approaches to terrorism, which experts like Goodman believe would likely produce different results.