To help you understand this exercise, let's go through each of the sentences and how we order the words:
This is a boring tour.
This sentence has a subject 'This' and a verb 'is.' The adjective 'boring' describes the noun 'tour.'
I like these birds.
The subject 'I' is followed by the verb 'like.' 'These' is a demonstrative adjective describing the noun 'birds.'
These are my sisters.
'These' is the subject of the sentence, and it is followed by the verb 'are.' The possessive pronoun 'my' describes the noun 'sisters.'
I'm watching this video.
The contracted subject and verb 'I'm' (I am) indicate the action, followed by the present participle 'watching' and the object 'this video.'
These animals are really funny.
'These animals' is the subject, followed by the verb 'are' and the subject complement 'really funny,' which describes the subject.
This vacation isn't expensive.
'This vacation' is the subject. 'Isn't' is the contraction of 'is not,' followed by the adjective 'expensive,' which describes the subject.
These sentences help us understand how to structure simple sentences with demonstratives like 'these' and 'this' along with adjectives and verbs.