Answer:
1. Scanner = reading passports.
2. Barcode reader = automatic stock control.
3. pH sensor = monitor soil in a greenhouse.
4. Microphone = voice recognition.
Step-by-step explanation:
1. Scanner: Copies paper documents and converts the text and pictures into a computer-readable form. Therefore, it can be used for reading passports.
2. Barcode reader: reads labels containing parallel dark and light lines using laser light or LEDs; the width of each line represents a binary code. Therefore, it is used for automatic stock control.
3. pH sensor: detect changes in acidity levels; data is often in analogue form. Thus, it is typically used to monitor soil in a greenhouse.
4. Microphone: allows audio signals to be converted into electric signals; these can be interpreted by a computer after being converted into digital form. Microphones are used for voice recognition.