High pitched sound: Whistling:: Low pitched sound: ..........
A) Roar of a lion
B) Woman’s scream
C) Chirping of birds
D) Crying of babies

Hint: The Pitch of a sound is one of the characteristics of the musical sound or the note. The note measures the difference between the bass note and the high note. The note of high frequency has a high pitch and vice versa. If a sound vibrates much it becomes the high-pitched sound and the sound that vibrates less is low-pitched.

Complete step by step answer:
The three characteristics of a musical sound or a Note is as follows:
LOUDNESS: The loudness is the feeling of a faster sound wave that reaches the ears. The loudness is high for a large amount of the energy reaches the listener’s ear.

PITCH: The note measures the difference between the bass note and the high note. It is generally referred to by the sensation of a frequency. If a sound vibrates much it becomes the high-pitched sound and the sound that vibrates less is low-pitched. Hence, the note of high frequency has a high pitch and vice versa.

QUALITY or TIMBRE: Quality can make the difference between the notes of the same loudness and pitch.

Here in the problem given that, higher-pitched sound: whistling:: Low pitched sound: …………………..
We have to fill in the blanks.
higher pitched sound: whistling means - the higher-pitched sound is related to whistling.
We need to figure out from the given options which are related to the lower-pitched frequency.
Option A. – Lion’s roar has a lower frequency and so is a lower-pitched sound.
Option B. – Women’s screaming is a high-pitched sound.
Option C. – The chirping of a bird has a high frequency.
Option D. – The crying of a baby sometimes has a very high pitch.

Hence, the right answer is in option (A).

Note: The examples of higher-pitched sound are –
1. Chirping of bird
2. Women’s loud voice
3. Whistling
4. Baby’s crying

The examples of lower-pitched sound are –
1. Dog’s barking
2. Lion’s roar
3. Sound of a drum.