Answer:
1. Es triste que muchos ríos estén contaminados.
2. Es ridículo que algunas personas eviten reciclar.
3. Es una lástima que los turístas no recojan la basura.
4. Es extraño que la gente destruya el medio ambiente.
Explanation:
In this exercise you have to form sentences with the correct form of the verbs "estar", "evitar", "recoger", y "destruir". You have to conjugate the verbs.
1. It's sad that many rivers are contaminated. In this case the verb "estar" must be conjugated as "estén".
2. It is ridiculous that some people avoid recycling. In this case the verb "evitar" must be conjugated as "eviten".
3. It's a pity that tourists do not pick up the garbage. In this sentence the verb "recoger" must be conjugated and you should change letter "g" for "j" so the verb conjugated would be "recojan".
4. It's strange that people destroy the environment. In this case the verb "destruir" must be conjugated "destruya" so final "ir" is changed into "ya".