Answer:
A ballpoint pen that changes itself into a sword. The name of this pen / sword is Riptide
 
        
             
        
        
        
Answer:
The type of invention that interested the narrator's mother was to draw sketch of things such as spiral of co-rk-scr-ew, ha-n-dier handle, etc.
Explanation:
"Daughter of Invention" is a short story written by Ju-lia Alv-arez. The story is about Cu-ckita and her mother, who is accustomed to inventing something every night. 
The narrator mentions that her mother used to create every night, in the corner of her room, as if a scholar burning the midnight oil. She used to draw sketched of various things in the notepad brought by Cu-ckita's father from office. 
 
        
             
        
        
        
Answer:
It's tough to be the youngest.
Explanation:
The infinitive form of a verb is the verb in its basic form. It is most times started with 'to', and then the base verb follows. It could also simply just be the verb in it's base form. A gerund is the -ing form of a verb. So, in the sentence above, the gerund is 'being'. 
Therefore, to convert this sentence to the infinitive form, the gerund, 'being' will be converted to its base form, -be. When 'to' is attached to it, it becomes the infinitive, -to be.