Question

Подчеркните инфинитив в данных предложениях,укажите их синтаксическую функцию в предложениях:1.We saw the guests enter the house.2.It began raining.3.Would you be so kind to lend me your umbrella?

Answer 1

В первом предложение инфинитива не вижу. 
Во втором  it began raining - после ит два слова, это герунди.
А в третьем предложении начиная с be so kind to lend - инфинитив.

Answer 2

1. We saw the guests enter the house. - The infinitive in this sentence is "to enter." - The syntactic function of the infinitive is to serve as the direct object of the verb "saw." It answers the question "what did we see?"

2. It began raining. - The infinitive in this sentence is "to rain." - The syntactic function of the infinitive is to serve as the subject of the verb "began." It answers the question "what began?"

3. Would you be so kind to lend me your umbrella? - The infinitive in this sentence is "to lend." - The syntactic function of the infinitive is to serve as the complement of the adjective "kind." It answers the question "what kind of action would you be so kind to do?"

Note: In English, the infinitive form of a verb is typically written with the word "to" before the base form of the verb (e.g., to see, to enter, to rain, to lend). Identifying the infinitive in a sentence can be helpful for understanding its grammatical structure and the role of different words and phrases within the sentence.