Answer:
a. So long as, after reaching the age of majority, Sally did not state orally or in writing that she intended to be bound by the contract, then she did not commit an express ratification.
Explanation:
Express ratification is a direct affirmation from a certain person that can be used to confirm a set of criteria needed to enter a certain contract/agreement.
In the case above, the sellers know that Sally was under the age of 18.
This mean that they're aware that at the time of the purchase, Sally was not legally capable to be binded by a contractual agreement. This mean that Sally can basically void all of the contract made with those sellers.
One exception exist under such circumstances.
Sellers can still make contract with underage people as long as that underage people promise to fulfill their end of the contract by the time they reach legal age.
But in the case above, Sally made none of such promise both orally or in writing. This mean she's not bounded by express ratification that legally require her to fulfill the contract she made when she's underage.