[ Adjective + to + Verb ]
it’s difficult to understand
A. a dog
B. a plane
C. an English book

Random Topics:
Relative Clauses beginning with PrepositionsPast Tense and Perfect Tense1st and 2nd ConditionalsConjunctions and Verb TensesModal Verbs for Permission and ObligationConjunctions in Complex Sentencesa, an, the, zero articleAdverb Clause ConnectorPossessive PronounsGerunds and InfitinitivesOther quiz:
Relative Clause › ViewThe woman _____ daughter was crying tried to calm her down.
A. Whom
B. Which
C. Whose
D. Who
Prepotitions › View
married
A. to
B. with
C. of
Tenses › ViewLook out! We __________ crash!
A. are going to
B. will
C. shall
Grammar › View
a premise that is untrue or distorted
A. premise
B. false premise
C. faulty reasoning
D. false consensus