Encuentra el sujeto real: ignora lo que va entre comas y los grupos con “of…”.
Posesivo plural: researchers’ (solo apóstrofo). Posesivo singular: researcher’s. Its = de él/ella (cosa); it’s = it is.
Una frase introductoria (“Walking to school, …”) debe ir seguida de quien realiza la acción.
Estrategia paso a paso
Lee la frase con cada opción en voz baja y busca pistas de tiempo (“in 1969”, “by the time”, “since”).
Nombres colectivos (council, team, committee) son singulares: its, has.
Trampas habituales
Concordar el verbo con el sustantivo más cercano en vez de con el sujeto.
Frases invertidas: “Beside the door stand two chairs” (el sujeto, “chairs”, va después del verbo).
Ejemplo resuelto
“The list of ingredients is long.” → el sujeto es “list” (singular), no “ingredients”.
Preguntas de ejemplo
Intenta responder antes de abrir la solución. Las preguntas están en el idioma del examen.
Pregunta 1
Dificultad fácil≈ 1 min
Both the violin and the cello displayed in the music museum’s main gallery ______ made by the Italian instrument maker Antonio Stradivari in the early 1700s.
Which choice completes the text so that it conforms to the conventions of Standard English?
AA. was
BB. is
CC. were
DD. has been
Ver respuesta y explicación
Respuesta correcta: C. were
Explicación
The subject “Both the violin and the cello” is plural, because two things are joined by “and.” The event happened in the 1700s, so the plural past-tense “were” is correct.
“Was,” “is,” and “has been” are singular forms.
Pregunta 2
Dificultad media≈ 1 min
After a series of spring floods, state engineers inspected the forty-two bridges in the river valley and found that most of ______ needed only minor repairs.
Which choice completes the text so that it conforms to the conventions of Standard English?
AA. it
BB. its
CC. them
DD. their
Ver respuesta y explicación
Respuesta correcta: C. them
Explicación
The pronoun refers to “the forty-two bridges,” a plural noun, and it is the object of the preposition “of.” The plural object pronoun “them” is correct.
“It” and “its” are singular. “Its” and “their” are possessive forms, which would need a noun after them (“their bridges”).
Pregunta 3
Dificultad difícil≈ 1 min
The intricate pattern of grooves and ridges pressed into the surfaces of the clay tablets, which archaeologists working at the site in the 1930s took to be purely decorative, ______ now thought to record a system of accounts for grain and livestock.
Which choice completes the text so that it conforms to the conventions of Standard English?
AA. are
BB. were
CC. is
DD. have been
Ver respuesta y explicación
Respuesta correcta: C. is
Explicación
The subject is the singular noun “pattern”; “of grooves and ridges,” “the clay tablets,” and the long “which” clause only describe it. “Now” calls for the present tense, so the singular present “is” is correct.
“Are,” “were,” and “have been” are plural and agree with the nearby plural nouns rather than with the subject “pattern.”