In a company,all users are using the Standard User profile in Salesforce. You have recently created a custom object; going forward, some users will require access to that object. How would you grant the required access to users?

Answer options:

A.Set access on the custom object in order to grant access to the users
B.Create a new profile, granting relevant access to the object, assign it to the relevant users
C.Modify the Standard User profile to grant relevant access to the object
D.Create a permission set granting access to the object, assign it to relevant users

Correct Answer: B 
You can’t edit the object permissions on a standard profile. However, you can clone an existing profile, and use that as the basis for a new profile, adjusting the apps and system settings as needed. Every organization includes standard profiles. In Professional, Enterprise, Unlimited, Performance, and Developer Editions, you can use standard profiles or create, edit, and delete custom profiles. In organizations, where you can’t create custom profiles (such as Contact Manager and Group Editions), you can assign standard profiles to your users, but you can’t view or edit them. 
Other options are incorrect because you can’t edit the object permissions on a standard profile. 
Reference: 

https://help.salesforce.com/articleView?id=admin_userprofiles.htm&type=5