Don’t drop cigarette ash on the carpet. (tú)
Odd that it’s “la alfombra” and not “el alfombra”. I was taught that some words like “el agua” have a masculine article so that the “la” and “a-” don’t awkwardly run together. But I guess this rule is not consistent.
The rule is mostly consistent, it’s just not like you describe it.
The rule is that the feminine article is ‘el’ when the noun begins with stressed ‘a’. This ‘el’ and ‘la’ both come from Latin ‘illa’ which became ‘el’ before stressed ‘a’ and ‘la’ elsewhere.
‘Alfombra’ is stressed on the ‘o’, so the rule doesn’t apply.
‘El águila’, ‘el hacha’, ‘el alta’, but: ‘la acera’, ‘la altura’, ‘la agonía’.