Which of the following could result in secondary succession?
the formation of a tall sand dune on a previously grassy beach
a vast glacier in motion forming a u-shaped valley on its wake
a volcanic eruption that covers most of what used to be a forest
an introduced species that devastates native plants as it feeds

By definition, a secondary succession usually takes lace when a when a community undergoes certain changes after it is previously colonised leading to its destruction. A common example of which is the third choice "a volcanic eruption that covers most of what used to be a forest."

Humid continental climate is found in the interior of continents between the 30 and 60 degrees latitude, but usually above the 40 degree line.   40 degrees north of the equator means less direct sunlight and therefore less warmth.   this climate is mainly found in the northern hemisphere since there are no major landmasses in the southern hemisphere.  if you live in northern indiana, you know all about humid continental because that is the climate type you have!