<h2>1. cuál</h2>
<em>¿</em><em>Cuál</em><em> aerolínea prefieren Uds? </em>
Since aerolínea, that translates into airline, is a singular noun, we need to use the word cuál that matches this type of nouns. If a question implies a choice between two or more alternatives and conveys the idea of selection, we must use the following formula:
<em>¿Cuál + singular noun?</em>
<h2>2. cuáles</h2>
<em>¿</em><em>Cuáles </em><em>canciones españolas conoces?</em>
Since canciones, that translates into songs, is a plural noun, we need to use the word cuáles that matches this type of nouns. So in this question I want to know <em>which Spanish songs do you know? </em>In this way, you might answer something like this:
<em>Yo conozco las baladas y las canciones de cumpleaños</em>
<h2>3. cuál</h2>
<em>¿</em><em>Cuál </em><em>tipo de libro le gusta?</em>
Since tipo, that translates into kind, is a singular noun, we need to use the word cuál that matches this type of nouns. So in this question le represents the indirect object pronoun either for the pronouns <em>él</em> and <em>ella </em>or usted (formal <em>you</em>). Perhaps I want to know either what type of books you or he (or she) would rather.
<h2>4. cuál</h2>
<em>¿</em><em>Cuál </em><em>tren toma él? </em>
Since tren, that translates into train, is a singular noun, we need to use the word cuál that matches this type of nouns. Here we want to know what train he takes. So <em>toma </em>is the conjugation of the verb <em>tomar (to take) </em>for the third person singular in the simple present. In this sentence, this person is <em>él </em>that matches <em>he </em>in English.
<h2>5. cuáles</h2>
<em>¿</em><em>Cuáles </em><em>diarios compran ellos? </em>
Since diarios, that translates into newspapers, is a plural noun, we need to use the word cuáles that matches this type of nouns. Here we want to know what newspapers they buy. So <em>compran </em>is the conjugation of the verb <em>comprar (to buy) </em>for the third person plural in the simple present.
<h2>6. cuáles</h2>
<em>Me gustan estos diarios. ¿</em><em>Cuáles </em><em>te gustan?</em>
In the question <em>¿Cuáles te gustan? </em>I must assume that the speaker asks me for the type of newspaper (diarios) I like to read. Since we are in this context and diarios is a plural noun, then we must choose cuáles. Moreover, te is the indirect object pronoun for the second person singular and gustan matches this person as well.
<h2>7. cuáles</h2>
<em>Ella escucha una canción puertorriqueña y una canción mexicana. ¿</em><em>Cuál </em><em>prefiere ella?</em>
This question implies a choice between two alternatives and conveys the idea of selection. Since the questions asks for an only selection (singular form), we need to choose cuál. On the other hand, <em>prefiere </em>is the conjugation of the verb <em>preferir </em>for the third person singular in the simple present. Here this person is <em>ella</em> that is feminine and means <em>she.</em>
<h2>8. esta</h2>
<em>Me gusta </em><em>esta </em><em>corbata</em>
This question stands for demonstrative adjectives. So these adjectives demonstrate a quality about the noun they modify. Here that quality is the<em> location</em> in respect to the speaker or the listener. So esta is used to point out something near to the speaker in space or time.
<h2>9. esa</h2>
<em>Me gusta </em><em>esa </em><em>corbata</em>
This question also stands for demonstrative adjectives. Since you like the tie farthest from you, then the demonstrative adjectives you must use is esa. This indicates something more distant, that is, nouns that are further from the speaker but they can be close to the listener.
<em><u>Note.</u></em><em> </em><em>You can also use </em><em>aquella </em><em>if the tie is far away from both the speaker and the listener.</em>