下列关于变异的叙述正确的是

目前，对新疆人口、城市分布影响最大的自然地理因素是（    ）

Betty：Hi, Mum!

Mum：Hello, Betty! Where are you now?

Betty: I'm____ (stand) on the Great Wall of China and____ (talk) to you. Mum：Really? That's great.

Betty：We're on a school trip.

Mum: What about the____(other)? Are they with you?

Betty: Well, right now Tony is ____(eat) a delicious ice cream. Wang Hui is ____take) lots of photos. Daming ____(have) lunch in the sun. And just now Lingling _____(buy) a few presents and postcards. Because they ____(be) on sale in the shop.

Mum: I'd like a postcard too, and please take some photos of the Great Wall and send____(they) to me by email.

Betty: OK. We're enjoying the school trip a lot. Anyway, it's time____(go) back to school now. Bye, Mum!

Mum：Bye, Betty!

我国境内发现的距今约170万年的原始人类是 (  )