Read passage 1 and answer the questions following the passage.

1Transfusion of a persons' own blood is called autologous transfusion. 2It's different from transfusion of blood given by others homologous transfusion, and transfusion of blood given by friends or family-directed donation.

3The public's growing interest in AIDS increases its interest in blood transfusion. 4It also leads some people to worry about receiving donated blood. 5Public concern about spreading disease through blood transfusion has increased the number of autologous transfusions. 6This trend promotes research and progress in autologous transfusion

7Now many people believe that a person's own blood is the safest blood to receive

8Advances in medicine continues to reduce the risk of transmitting viruses, such as human immunodeficiency virus (HIV), through blood. 9Research steadily finds new ways to test blood for disease, and blood donated by volunteers is becoming a safer product.

10Medical professionals often suggest autologous transfusion. 11They want the people to know that it is a choice they might have when they need blood. 12They encourage people to receive their own blood because it reduces possible negative effects of transfusion, 13 Receiving one's own blood ensures that the blood is compatible.

14 Transfusion of autologous blood avoids many types of transfusion reactions. 15Transfusion of directed donation blood does not prevent these reactions. 16 However, it’s difficult to change public Perceptions about this. 17 Many people still believe that receiving blood donated by family and friends prevents disease transmission. 18 Sometimes people choose not to donate blood.

19 Autologous transfusion is not always the best medical treatment. 20 Sometimes blood loss does not require transfusion. 21 It is impractical for large numbers of people to donate 'blood for the possibility of receiving it. 22 Also, some people who want to donate blood do not meet medical guidelines for donation.

Which sentence includes an incorrect form of verb?