Because it is difficult to trace hackers, exactly who isbehind any specific attack and how and where they operate remains to alarge extent a mystery, technology experts say.

技术专家说，因为黑客很难追踪，所以谁是攻击的幕后黑手很难确定，他们在哪里以及如何发动的攻击在很大程度上也都是谜。

youdao

It is very difficult to say when and where the first lamp was used, but they are mentioned in all three early ages - lamps were used in Egypt, Greece, and Rome.

台灯起源的时间和地点已无从得知，但是最早的3个时期都有台灯的记载——埃及，希腊和罗马。

youdao

It is not difficult to have conversations in Greece where people say they never imagined that joining the EU would result in outsiders dictating policies to them.

BBC: Greece euro crisis: Most dangerous moment

"It's difficult to say exactly how much debris is expected to show up, and when and where, " said Dianna Parker, a spokeswoman with the NOAA Marine Debris Program.

MSN: When Will Japan's Tsunami Debris Hit North America?

It is difficult to say how far this trend towards satire and self-parody will run in a world where politicians appear to be less powerful and when they agree with each other on so many issues of substance.

BBC: Kebabbed: Part 4