<span>"It's doubtful she will come."
The subjunctive is used to indicate some feeling towards a subject or uncertainty.
In the first sentence, the verb "know" is used. If someone "knows" something then it is right to them, and the subjunctive is not used.
In the second/third sentences, the adjectives true and certain are used. (Both of which are apparently synonyms to each other.) Since that there is certainty in these two examples, the subjunctive isn't used once again.</span>
Answer:
1 Yo soy alto y moreno
2 roberta está feliz hoy
3 los estudiantes están enfermos
4 usted no está aquí
5 mi libro está encima de la mesa
6 Marcos y liliana son hermano y hermana
7 mi padre es profesor
8 Martha es simpática, inteligente y creativa
9 son las diez y media de la mañana
10 hoy es lunes
11 mis amigos y yo estamos estudiando para el examen de español
