Dan buys a glass tea cup from a houseware store. The first time Dan pours hot water into the tea cup, the glass shatters, and one of the shards slices Dan's hand, causing severe injury. The glass itself is destroyed. What piece of evidence would be most helpful to Dan in bringing a suit against the houseware store?

Expert testimony that well$-$made glass tea cups of this type do not normally shatter when filled with. boiling hot water.

A salesperson from the houseware store who testifies that he told Dan that the tea cup had been previously used and was being as being sold $\text{'}$as$-$is$\text{'}.$

The design specifications from the manufacturer of the tea glass

Testimony regarding quality control at the tea glass manufacturer's production plant