To solve this problem, the user needs to know basic arithmetic and the concept of percentages and division. The user must multiply 1000 by 45%, then divide the result by 10.

First, let's calculate 1000 multiplied by 45%: 1000 x 45% = 1000 x 0.45 = 450

Next, let's divide 450 by 10: 450 / 10 = 45

Therefore, the answer is 45, which is option B.

Option A (35) is incorrect because it is not the correct result of the calculation.

Option B (45) is correct because it is the result of the calculation.

Option C (3.5) is incorrect because it is not the correct result of the calculation.

Option D (4.5) is incorrect because it is not the correct result of the calculation.

The Answer is: B. 45