I am a little confused. The lesson says that in the negative, de l' becomes d' (in front of a vowel or silent h). However, the example given: C'est de l'huile d'olive ? -Non, ce n'est pas de l'huile d'olive.
Shouldn't it then be: Ce n'est pas d'huile d'olive.
In a related doubt, are these sentences correct:
Tu as de l'argent? Non, Je n'ai plus de l'argent. (Do you have some money? No, I do not have any money.)
or should it be: Non, je n'ai plus d'argent.