Final answer:
The verb 'is' in the first sentence should be changed to 'are' to match the plural subject 'stockholders'. The verb 'was' in the second sentence should be changed to 'were' to match the plural subjects 'a box of chocolates' and 'a carton of ballpens'.
Step-by-step explanation:
In the first sentence, the verb 'is' should be changed to 'are' to match the plural subject 'stockholders'. The revised sentence would be: 'The majority of the stockholders are eligible to buy some stocks.'
In the second sentence, the verb 'was' should be changed to 'were' to match the plural subjects 'a box of chocolates' and 'a carton of ballpens'. The revised sentence would be: 'A box of chocolates and a carton of ballpens were given to each con.'