English Grammar and Usage

It contains a gerund ‘flowing’.

It is passive voice of simple past tense.

It is present perfect continuous tense. 'Subject + has/have + been + present tense verb + ing + since/for'.

It refers to an action that happened before another action in the past.

"Drop in" (or "drop by") means to pay a brief, informal visit without an appointment or prior arrangement. The other options are incorrect: "drop out" means to withdraw or quit, "full back" appears to be a typo (likely for "fall back"), and "full In" contains a capitalization error.

Le pronom relatif 'où' s'emploie comme complément circonstanciel de lieu ou de temps. Alors c'est le bon choix.

Le pronom relatif 'que' est complément d'objet direct. Alors c'est le bon choix.

until he arrives -- upto the time he arrives

Option 3 is the correct usage. It is an interrogative case, so (?) is needed. Moreover, reported speech needs to be inserted in inverted commas.

It is in present continuous tense as is/am/are + v1 + ing has been used here.

Past of past is reffered to in the sentence and had + v₃ has been used. Hence, option 3 is the correct answer.

The sentence is in the past continuous as was + V1 + ing has been used here.

A question has been asked, so it is an interrogative sentence. Hence, option 1 is the correct answer.

When using reported speech with 'said' (past tense), the verb in the subordinate clause must be in the past perfect tense to show it happened before the speaking. 'Had been' correctly indicates the action was completed prior to the past moment of speaking.