What one language would you encourage Americans to learn, and why?

The language that they want to learn and would find the most useful to them.

Let's face it, English is the most-learned second language around the world because it is useful to just about everyone. There is no one comparable second language for English-speakers.

I think it would be ideal if some Americans learned Spanish, others learned Mandarin, and still others learned Arabic, Russian, Korean, and so forth.

But to pick one of those to be "the" second language for all Americans to learn would be a mistake, in my opinion.

I wouldn't. Multiple languages cause social disturbances (eg Quebec secessionists in Canada, Welsh speakers in the UK, Catalans in Spain, etc), inefficiency and confusion - what does it cost the EU to translate every doc't into 2 dozen (or whatever) different languages.

A much better solution would be to have everybody speak American.

What programming languages are most used by tech giants like Google, Facebook, Microsoft etc?

Almost all large scale desktop software is written in C++.You can usually determine the compiler and language of an executable by viewing it in a hex editor, dependency viewer or similar tool.I read an article where the author analyzed a Windows Vista installation and found a

Can a hacker be paid to hack credit scores on all three of the credit agencies?

I'll take it one step further and say that you may not spot a secret agent. Think about it. These are people who have been selected for their ability to blend in and not draw attention. They have months/years of intensive training in the fine details of avoiding suspicion and detection.

What does 'mobile only deal' mean in AliExpress?

Mobile only deal means if you can get that price in Aliexpress app which is lower than PC. That's a marketing strategy encourages people order via Aliexpress app instead of PC.