What policy did Kirstjen Nielsen claim US law enforcement was simply carrying out?

Choices:
A. policies intended to control the crime rate
B. not enough information
C. the 'zero-tolerance policy' towards illegal immigrants
D. policies regarding treatment of whistleblowers
the 'zero-tolerance policy' towards illegal immigrants
WHITE HOUSE — An audio recording was released Monday depicting children desperately crying and begging for their parents after being separated from them by U.S. immigration authorities at its southwestern border, sparking new outrage against the Trump administration and its new "zero-tolerance policy" towards illegal immigrants.
The nearly eight-minute long recording was released by ProPublica, an independent, investigative news site. ProPublica says an unidentified whistleblower passed on the recording to a civil rights attorney, who gave it to the website.
Among the disturbing sounds heard on the recording was a child identified by ProPublica as a six-year-old girl from El Salvador begging authorities in Spanish to call her aunt to pick her up from the detention center.
At one point in the audio, a man identified as a Border Patrol agent said in Spanish over the cries of scores of children: "Well, we have an orchestra here. What's missing is a conductor."
President Donald Trump defended his administration's policy of forcibly separating children from parents at the U.S. border with Mexico on Monday, saying “The United States will not be a migrant camp and it will not be a refugee holding facility."
Trump, speaking in the White House East Room during a National Space Council meeting, warned that “what’s happening in Europe … we can’t allow that to happen to the United States – not on my watch.”
Earlier in the day, on the Twitter social media platform, the president inaccurately linked migration in Germany to a rising crime rate. (Actually, the latest German government statistics show reported crimes at the lowest level in 30 years.)
Nearly 2,000 children were sent to mass detention centers or foster care from mid-April to the end of May, according to government officials.
The regular White House briefing was delayed several times Monday amid the furor as officials huddled with Trump in the West Wing.
Press Secretary Sarah Huckabee Sanders finally introduced Department of Homeland Security Secretary Kirstjen Nielsen by late evening, and she defended the administration’s “zero-tolerance” policy that is breaking up families at the southwestern U.S. border.
Nielsen forcefully pushed back at the negative media coverage, asserting that what U.S. authorities are doing is properly enforcing the law.