Fill in the gaps: Wir müss.... heute .... Hausaufgaben für unser.... Deutschlehrer machen.

Antwort: Wir müssen heute die/unsere Hausaufgaben für unseren Deutschlehrer machen.
Gap 1 = Wir müssen - the modal verb müssen = to have to. Because the subject in this instance is 'wir' meaning 'we' is plural, the verb is conjugated to reflect this. Müssen is conjugated like this: ich müsse, du musst, er/sie/es muss, wir müssen, ihr müsst, sie/Sie müssen.
Gap 2 = die/unsere. Either is applicable, what is important is the recognising that the noun 'Hausaufgaben' , meaning 'homework' is plural, meaning that the article will be 'die'.
Gap 3 = The preposition 'für' meaning 'for' is an accusative preposition, that changes the masculine article 'der' into 'den', because the noun Deutschlehrer (German teacher) is masculine, this comes into play here. In this sentence, rather than having the article 'der', we have the pronoun 'unser', meaning 'our'. In this instance, the accusative preposition will change the ending of unser to unseren, reflecting the change that preposition brings about.This part is slightly complex at GCSE level, but is a helpful venture into the A-level curriculum. You will certainly have encountered German prepositions during GCSE but are likely to be unsure of how these prepositions often change the articles of nouns to reflect the case of the preposition. In addition, certain verbs will set the case of a sentence, but this isn't applicable here.