The interlaced lines for NTSC colour standard number: 

(A) 475 

(B) 500 

(C) 525 

(D) 550

Correct Ans: (C)

Explanation:

The NTSC (National Television System Committee) color standard uses 525 interlaced lines. These lines represent the total number of horizontal lines in each frame of the television system. The 525 lines include both visible and blanking lines, which contribute to the overall image.

In this system, interlaced lines mean that the image displays in two passes. In the first pass, the system draws the odd-numbered lines. Then, in the second pass, it fills in the even-numbered lines. This interlacing process improves display quality and enhances the smoothness of motion on older television sets.

Additionally, the 525-line format became widely used in North America and parts of South America. This usage set NTSC apart from other color standards, such as PAL and SECAM, which use different line counts. The NTSC standard also played a key role in the development of television technology during the mid-20th century.

However, modern television systems, such as HDTV, now use progressive scanning and higher line counts for clearer, more detailed images. Despite these advancements, the NTSC standard remains a significant milestone in television broadcasting history.

Therefore, the NTSC color standard uses 525 interlaced lines.