Verified answer

I'm not sure either but here's a bit of info I found from wikipedia:

Pandora had been given a large jar and instruction by Zeus to keep it closed, but she had also been given the gift of curiosity, and ultimately opened it. When she opened it, all of the evils, ills, diseases, and burdensome labor that mankind had not known previously, escaped from the jar, but it is said, that at the very bottom of her box, there lay hope.

Here's the answer to your question: (from an online encyclopedia)

Hesiod tells us, "the earth and sea are full of evils" (101). One item, however, did not escape the jar (96-9), hope.

Only Hope was left within her unbreakable house,

she remained under the lip of the jar, and did not

fly away. Before [she could], Pandora replaced the

lid of the jar. This was the will of aegis-bearing

Zeus the Cloudgatherer.

I hope I answered your question.