What's the most logical way to complete this passage?

Hundreds of British Muslims have travelled to Iraq to fight for the extreme jihadist group ISIS, terror experts have said. The Government believes more than 500 British citizens have left the UK and gone to join rebel fighters in Syria, with many of them feared to have crossed the border to join the uprising in Iraq. The ruthless ISIS (Islamic State in Iraq and Syria) extremists control large areas of land in Syria and are now turning their attention to Iraq and particularly Baghdad, having already taken the cities of Mosul and Tikrit. Meanwhile, British security experts are also looking at the possibility that home-grown extremists trained by the ultra-violent group may bring terror back to the UK.

The best way to help
Syria people is by donating to UK-registered charities.'