Which phrase correctly completes this opinion. je les rebouteux aient la connaissance des maladies. a) ne doute pas que b) suis certain que c) ne suis pas sûr que d) pense que

Any french speakers? i need some . could someone check the grammar of my french translations? 1. i would get a card for a bookstore. > > > *je voudrais acheter une carte-cadeau pour la librairie en le centre commercial.*2. they would have to go to the bookstore, the jewelry store, and flower shop. > > > ils devraient aller à la librairie, la bijouterie et le fleuriste.3. a good amount to spend would have to be a few hundred dollars. > > > un bon montant à devrait être de quelques centaines de dollars.4. i decide what present i am going to get for a person by thinking about what would be important to them. > > > je décide quel cadeau je vais chercher pour une personne (by thinking about) ce que cela important pour leur.for the 4th question, how would i say "by thinking about" in french? and by the way, i need the french sentences checked, those are what i wrote.