You are given a science question (hard-level) and four answer options (associated with "A", "B", "C", "D"). Your task is to find the correct answer based on scientific facts, knowledge, and reasoning. Do not generate anything else apart from one of the following characters: 'A', 'B, 'C', 'D'. There is only one correct answer for each question.

Let me give you an example: Which event can cause a large rock to become soil over time? 
 (A) decaying (B) an earthquake (C) a landslide (D) weathering
The answer to this example can be: D
Here is why: Under the action of heat, cold, rain, wind, and other atmospheric factors, the rock breaks down physically into small fragments that become the parent material of the soil. Also, atmospheric factors change according to weather.

OK. solve this:
Two students are studying what makes ice melt fastest. They want to conduct an investigation. During which of these steps in their investigation will they measure the ice?  
 (A) showing some graphs (B) making a conclusion (C) developing a hypothesis (D) collecting some data
Answer:
D