Why does a curve on a distance-time graph indicate acceleration?

A curve on a distance-time graph indicates distance with respect to time.

For someone good in interpreting curves, the slope of distance/time at each point on the curve represents the velocity.

For someone still better in reading curves, the second derivative of the curve at any point indicates acceleration. Second derivative means the rate of variation of velocity with respect to time.

So the quick answer is a curve on a distance time graph does NOT directly indicate acceleration. See example in attached diagram. If you can "see" the constant acceleration indicated in the bottom (distance-time) graph, then yes, you can find acceleration from a distance-time graph. Otherwise, the answer is still no.

littering streams           is the answer

the correct answer is - d. china has a large and growing population.

the fact that china has a large (the biggest) population, and it is still growing, doesn't hinder the agriculture production in the country. in fact, it can for increased production in the agriculture, since there's more labor force, as well the sheer mass of people produces lots of scientists that come up with new inventions as to how to improve this sector. nice example is the inner mongolia region in china, in general dominated by the gobi desert, but few scientist came up with a nice idea as to how to make the region productive by using plants that are very resistant to droughts, so lots of people have been employed, and the region is becoming greener and greener each year, and the production of food in this region is also increasing.