Answer:
A
Step-by-step explanation:
 The sentence in option A uses possessive/ genitive case correctly. The first noun sisters  is plural ending in s , so it is correct to use a simple apostrophe ( ' ) after the noun. Charity  is a singular noun: addind 's is correct. Children is a plural noun not ending in s , so it is correct to form the possessive by adding the apostrophe and the s ('s) to it.