Since it's declarative, it ends with a period. We should add some commas as well.
<em>S</em>chool began on a cold<em>,</em> <em>S</em>eptember morning<em>.
</em>
That should work.
I think your answer will be D
This is the Gerund: Gerund is formed by adding -ing to the verb stem: for example: do-ing; mak-ing, kiss-ing.
It can be used as a noun, but also in other positions, but here is an example for the noun use:
Kissing Paul was a good idea.
