Definition: In this task, you will be presented with a passage and have to answer a question based on your understanding of the events inferred from the passage. Try to find the best answer that is most likely to fill in "_". Note that the URLs in the text have been replaced with [Link].
Input: A terror plot linked to Islamic State is identified in the West every fortnight, a major report has revealed. At least 32 attacks inspired by the Islamist group were either carried out or thwarted since July last year, according to new research. The plots were detected in 10 countries, including three in Britain, a study by the Henry Jackson Society think-tank revealed. The report, published today, comes after ministers launched a crackdown on four notorious British jihadists who have travelled to Syria to lure sympathisers into causing carnage on UK streets. So-called ‘Mrs Terror’ Sally Jones, 46, privately-educated Aqsa Mahmood, 20, ex-medical student Nasser Muthana, 20, and former security guard Omar Hussain, 27, were placed on a UN blacklist.Isis terrorists have attempted one terror attack in the West a fortnightAt least 32 plots were either carried out or thwarted since last JulyThe Henry Jackson Society warned returning terrorists were a major threatAt least three planned terror attacks in Britain have been foiled by police 
 Question:Earlier this month, the head of MI5 warned that _ was facing an unprecedented terror threat with home-grown fanatics are being radicalised to the point of violence within weeks.

Britain