In a colony of 60 people, the language spoken by each person is noted. 10 speak only Bengali, 5 speak only Assamese, 10 speak Hindi and Odia, 12 speak Marathi and Hindi, 13 speak English, Tamil and Ma

Total people in the colony = 60.

• Only Bengali speakers = 10
• Only Assamese speakers = 5
• Hindi and Odia speakers = 10
• Marathi and Hindi speakers = 12
• English, Tamil, and Marathi speakers = 13
• Assamese and Hindi speakers = 5

Sum of people in known categories = $10 + 5 + 10 + 12 + 13 + 5 = 55$.
The remaining people speak both Bengali and Hindi.
Remaining people = Total people - Sum of known categories
Remaining people = $60 - 55 = 5$.
So, Bengali and Hindi speakers = 5.

Bengali speakers include those who speak only Bengali and those who speak Bengali and Hindi.
Total Bengali speakers = (Only Bengali speakers) + (Bengali and Hindi speakers)
Total Bengali speakers = $10 + 5 = 15$.

Marathi speakers include those who speak Marathi and Hindi, and those who speak English, Tamil, and Marathi.
Total Marathi speakers = (Marathi and Hindi speakers) + (English, Tamil, and Marathi speakers)
Total Marathi speakers = $12 + 13 = 25$.

Ratio = (Total Bengali speakers) : (Total Marathi speakers)
Ratio = $15 : 25$.

Divide both numbers by their greatest common divisor, which is 5.
Ratio = $\frac{15}{5} : \frac{25}{5} = 3 : 5$.

The ratio of Bengali speakers to Marathi speakers is $3 : 5$.

The correct option is (D).

$\boxed{\text{D}}$