You could put the Visitor in 3rd person.
however some visitors can be despoiled by the escorts
The visitors were very gracious towards their host.
He was evidently touched by the plight of poor visitors.
visitors were coming so she worried about the cleanliness of her house
Her exceptional hospitality made the visitors feel like home.
Visitor's or Visitors'... The apostrophe in this case is possessive, in that the washroom belongs to the visitor (in the first case), or the visitors (in the the 2nd case). I think the safest bet would be to go with Visitors' .
The simple subject is "visitors". "Many" is an adjective modifying "visitors"
Beginning with a short tour, visitors can learn and experience all that the Science Center has to offer.
A recluse is a person who lives a solitary life and avoids other people. Example sentence: The 5th Duke was an eccentric recluse, who shunned visitors.
sentence three has 2 errors
"All visitors to the factory" is the complete subject.
It is not a sentence.