1 metre is equal to
$A.\text{ }{{10}^{-10}}\overset{\circ }{\mathop{A}}\,$
$B.\text{ }{{10}^{8}}\overset{\circ }{\mathop{A}}\,$
$C.\text{ }{{10}^{6}}\overset{\circ }{\mathop{A}}\,$
$D.\text{ }{{10}^{5}}\overset{\circ }{\mathop{A}}\,$

Hint: Angstrom (Å) is a unit of length used mainly in measuring wavelengths of light. This unit is named after the Swedish physicist Ander Jonas Ångström. Although the unit is recognized worldwide, it is not an International System of unit (S.I.) or metric unit.

Complete answer:
Angstrom is named for Swedish physicist Anders Jonas Ångström, who used it to construct a chart of the wavelengths for electromagnetic radiation in sunlight in the year 1868. His use of this unit made it possible to record the wavelengths of visible light (4000 to 7000 Å) without using decimals or fractions. The chart and unit became used widely where we deal with extremely small structures such as solid state physics, solar physics, atomic spectroscopy, etc.

Angstrom is defined as the metric unit of length which equals ${{10}^{-10}}$ m (one ten-billionth of a metre, 0.1 nanometre, or 100 picometres).

So, the correct answer is “Option A”.

Additional Information:
The different units of length and their conversion charts are given below:
1 millimetre (m) = 0.001 metre (m)
1 centimetre (cm) = 10 millimetres (mm)
1 centimetre (cm) = 0.01 metre (m)
1 decimetre (dm) = 10 centimetres (cm)
1 decimetre (dm) = 0.1 metre (m)
1 metre (m) = 10 decimetres (dm) = 10 cm = 1000 mm
1 decametre (da) = 10 metres (m)
1 hectometre (hm) = 10 decametres (da) = 100 m
10 hectometres (hm) = 1 kilometre (km) = 1000 m
$1\text{ }nanometre\text{ }\left( nm \right)\text{ }=\text{ }{{10}^{-9}}metre\text{ }\left( m \right)$
$1\text{ }Fermi/femtometre\text{ }\left( fm \right)\text{ }=\text{ }{{10}^{-15}}metre\text{ }\left( m \right)$
$1\text{ }Angstrom\text{ }\left( \overset{{}^\circ }{\mathop{A}}\, \right)\text{ }=\text{ 1}{{\text{0}}^{-\mathbf{10}}}\text{metre }\left( m \right)$

Note:
When dealing with numerical in Physics you need to specially memorize (or practice some numerical which involve this units)conversions like metre to Angstrom, metre to nanometre and metre to Fermi apart from the conversion of most commonly used units such as kilometre, metre, centimetre, milimetre, etc.