Which is the best definition of a complement, in grammar?

Im the following sentence, what is the complete subject . an old friend of mine is in the hospital

Bicycle riding should be encouraged, and adding bicycle lanes will increase the number of riders. it is healthier for people to ride than to sit angrily in traffic. it is healthier for everyone to breathe cleaner air. sharing the road can be tricky, but there are things that can be done. so, add the bike lanes and get rolling! which sentence would improve this conclusion? every town should consider adding bicycle lanes, because it is a great idea. organizing safety classes for drivers and cyclists will ensure that everyone knows the rules. do not listen to negative people who complain about anything new. it is true that some people might get injured, but even walking can be dangerous.

How are the two arguments made in the passages different? a. the first passage claims that pets in class will children with health problems; the second passage says pets will make some health problems worse. b. the first passage claims that students’ nervousness will decrease around pets; the second says that students’ nervousness will increase around pets. c. the first passage claims that pets will make the teacher’s work easier by keeping students busy; the second passage says pets will make the teacher’s work harder. d. the first passage claims that pets in school will be good for kids’ mental health; the second passage says pets will be bad for kids’ mental health.