She is capable __________ achieving great things.

• শূন্যস্থানে সঠিক উত্তর হবে - of.
Complete sentence: She is capable of achieving great things.

• Capable of doing something:
English Meaning: Having the ability, power, or qualities to be able to do something
Bangla Meaning: (ব্যক্তি) শক্তি-ক্ষমতাবিশিষ্ট; সম্ভাবনা আছে এমন; উন্মুখ।

Example sentence: 
- I know what you are capable of.
- The system is capable of change for the better.

Source: 
1. Cambridge Dictionary.
2. Accessible Dictionary by Bangla Academy.