The following bar graph represents the production of three types of buses by a company over the years (in thousands).

In which of the following years was the percentage production of B type buses to C type buses, the maximum?

The correct answer is 2015.

To find the year in which the percentage production of B type buses to C type buses was the maximum, we calculate the percentage for each year given in the options using the formula:
$\text{Percentage}=\left(\frac{\text{Production of B type buses}}{\text{Production of C type buses}}\right)\times 100$

From the given bar graph, the values for production of B type and C type buses (in thousands) for the given years are as follows:

1. For the year 2013:
Production of B type buses = 30
Production of C type buses = 25
$\text{Percentage}=\left(\frac{30}{25}\right)\times 100=120\%$

2. For the year 2014:
Production of B type buses = 27.5
Production of C type buses = 22.5
$\text{Percentage}=\left(\frac{27.5}{22.5}\right)\times 100=122.22\%$

3. For the year 2015:
Production of B type buses = 35
Production of C type buses = 22.5
$\text{Percentage}=\left(\frac{35}{22.5}\right)\times 100=155.56\%$

4. For the year 2016:
Production of B type buses = 22.5
Production of C type buses = 30
$\text{Percentage}=\left(\frac{22.5}{30}\right)\times 100=75\%$

Comparing the percentages obtained above, the percentage production of B type buses to C type buses was maximum in the year 2015 (155.56%).