Step 1: First Blank
Start-ups usually begin with fewer resources and networks. Hence the correct word is “Limited reach”. Words like “restricted” also fit partly, but “limited” is more natural and common.
Step 2: Second Blank
The connector should be “when” because the condition applies specifically at the time of introducing new products. “Since,” “while,” or “if” would make the sentence awkward.
Step 3: Third Blank
Start-ups thrive by creating innovative products. So “innovative” is the correct word, not “new” in this position.
Step 4: Fourth Blank
The result of innovative products is that start-ups open up new markets. Words like “innovative markets” or “restricted markets” don’t make sense here.
Step 5: Final Statement
Thus, the completed sentence is:
“While start-ups have limited reach, when they introduce innovative products, they open-up new markets.”
Final Answer:
\[ \boxed{\text{Limited, when, innovative, new}} \]