Final answer:
At the two-word phase, children struggle with word order in sentences.
Step-by-step explanation:
The correct answer is c) They struggle with word order. At the two-word phase, children have difficulty with sentences like "The car bumped the truck." This struggle with word order is a normal part of language development for children at this stage. They are still acquiring the rules of grammar and syntax, so they may have trouble putting words in the correct order in a sentence.