지문
a better way is to use a streak test. the color of a mineral in powder form is called its streak. streak can be measured in two ways. minerals can be dragged across a hard porcelain material called a streak plate or crushed into a powder. the former is the most common method for most minerals because it is easy and less destructive. the color of the mineral powder left on a streak plate is mostly unaffected by impurities because they do not strongly absob, transmit, or reflect light in a fine grain of the mineral. as a result, the color of the streak is a more reliable identifier than the color of the mineral. calcite, which can be many different colors, always has a streak that is white. the iron-based minerals hematite and magnetite often appear a similar dark gray and can sometimes be difficult to differentiate visually, but their streaks clearly differ. magnetite produces a dark gray streak. the streak of hematite, on the other hand, is a dark, reddish brown.

문제
which of the following can be inferred about the color of mineral streaks from paragrah?
(a) they cover the entire range of the color spectrum.
(b) they are only stable in minerals that do not require crushing.
(c) they lack the impurities found in large mineral chunks.
(d) they are sometimes the same color as the mineral.답이 (d)인데 지문속의 어떤 내용을 근거로 (d)의 내용이 추론될 수 있는지 궁금합니다!!