What is the channel spacing for MF-HF voice frequencies? (C). 3.0 kHz

The spacings must be confined in a band of ± 3 kHz above and below the frequency.

For more info please see in pdf, 47 C.F.R. § 2.106 FCC Table of Frequency Allocations

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What is the channel spacing for authorized F1B/J2B frequencies? D. 500 Hz

From 47 C.F.R. § 2.106
FCC ONLINE TABLE OF FREQUENCY ALLOCATIONS

5.57 The use of the bands 14-19.95 kHz, 20.05-70 kHz and 70-90 kHz (72-84 kHz and 86-90 kHz in Region 1) by the maritime mobile service is limited to coast radiotelegraph stations (A1A and F1B only).

Exceptionally, the use of class J2B or J7B emissions is authorized subject to the necessary bandwidth not exceeding that normally used for class A1A or F1B emissions in the band concerned.

Paragraph 5.57 on page 70

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You look up a frequency table and all the listings end in either .0 or .5 kHz. What kind of emission is used with these frequencies?
A. F1B/J2B SITOR (NBDP)

So, it is XX.0 or XX.5

Please see for more details, US Goast Guard National Weather Service page,

Section USCG HF SITOR (NBDP)

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How many SITOR (NBDP) signals can occupy the space of one voice signal? B. 6

Just remember answer six 6

For marine digital signals, namely narrow band printing NBDP or digital or digital selective calling is propagated at 1.7 kHz on the the upper side band SSB, with no carrier or lower side band.

For overall info, see US Goast Guard National Weather Service page,

Section USCG HF SITOR (NBDP)

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Radio emission mode occupies the most bandwidth
B. F3E

F3E emission mode is used for data transmission by the use of th radio wave in a single analog channel. The bandwidth is 180 kHz.

Code of Federal Regulations
Title 47 Telecommunication § 2.202 Bandwidths.
III-A. FREQUENCY MODULATION

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(C). J2B occupies least bandwidth.

J2B uses PSK31 (phase-shift key)

J2B emissions range from 110 kHz to 160 kHz, which is the 148.5 kHz in Region 1. Used in stations providing maritime mobile service.

For lots more details, see ICAO spectrum strategy, policy statements and related information

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