The problem occurs when people fail to join a group because they can get the benefits the group offers without contributing to the group’s efforts.

free-rider

Explanation:

In social context, there are many cases when a group's individual members can profit from each member's actions and all can benefit significantly from collective action. A free-rider refers to the individual who intends others to pay for a common good but plans to use the good themselves. However, if the number of free riders increases in a group common good can never be provided.

a is the final ! : )

the correct answer is the following is a list of inventions made in the medieval islamic world, especially during the "islamic golden age" (8th to 13th centuries),[1][2] as well as the late medieval period, especially in the emirate of granada and the ottoman empire.

science and technology in the islamic world adopted and preserved knowledge and technologies from contemporary and earlier civilizations, including persia, india, china, and greece-roman antiquity, while making a number of improvements and innovations.