1. Yo nunca _<u>HE TENIDO</u>_ (tener) problemas en mis viajes.
Explanation:
I have never had problems in my trips.
<em>Tener</em> is in infinitive, it means <em>to have.</em>
In this case you are refering to events in the past with continuity so you use the pretérito perfecto (past perfect) which is HE TENIDO.
That means that in the trips you have done over your life, there have not been any problems. The possibility of more trips in the future, and problems in them, is open.
Un is 'a,' masculine. Una is 'a,' feminine. Unos means 'some' or 'a few, ' masculine. Unas means 'some' or 'a few, ' feminine. That is just the answer. Enjoy
