"seule" refers to the woman, so it has to agree in gender and number with "femme". if it were about only one letter, the sentence would be : "la femme écrit une seule lettre". so in any case, there is no masculine noun in this sentence which would justify "seul" in the masculine form.
Hi sitesurf. One more qst: In the sentence, The woman sells vegetables, the translation is La femme vend DES legumes. Previously you have taught that les is used as a generality (and therefore meaning the woman sells (all) vegetables) and des would mean some here. When do we use LES and when do we use DES Grrr. so confusing :)
"des lettres" is the plural of "une lettre", just like "des légumes" is the plural of "un légume".
"des" is the plural indefinite article that English does not have and it is required to mean "more than one" before a plural countable noun.
"les lettres" is the plural of "la lettre", just like "the vegetables" is the plural of "the vegetable".
However, the indefinite article "les" has 2 functions:
introduce a specificity: "les légumes que tu vois ici" = the vegetables you can see here.
introduce a category or generality: "les légumes en général" = vegetables in general" (as a category)
In the sentence "la femme vend des légumes", she is selling more than one vegetable (like "some, several, a few, an unknown number of").
Both "combien de pain mange l'enfant ?" and "combien de pain l'enfant mange ?" can be said, because there is not much doubt that the bread cannot eat the child.
But you are right, with other nouns, there might be an ambiguity, in which case you will use the latter formula, as well as:
- Combien de pain l'enfant mange-t-il ? (formal)
- Combien l'enfant mange-t-il de pain ? (formal)
- Combien l'enfant mange de pain ? (standard)
- L'enfant mange combien de pain ? (standard)