Answer:
1. Lo
2. La
3. Las
4. Lo
5. Las
6. Lo
Step-by-step explanation:
That's because the direct object usually comes as te/me/lo/los/la/las/etc
And it usually replies to the question What? For example in the first sentence
1. Te lo cuento después.
What is she/he going to tell you later?
The answer is "lo" (which is used to replace something that has already been mentioned)
The same with the second sentence
2. ¿Cómo la puedo ayudar?
How can I help you/her?
Help what/who? Her - la